
LIBRARY OF CONGRESS. 

Chap. Gopyrighl No.. 

Shel£iS_k 



UNITED STATES OF AMERICA. 



An Electrical Library* 

By PROF. T. O'CONOR SLOANE. 

How to become a Successful Electrician. 

PRICE, $1.00. 

Electricity Simplified. 

PRICE, $1.00. 

Electric Toy Making, Dynamo Building, etc. 

PRICE, $1.00. 

Arithmetic of Electricity. 

PRICE, $1.00. 

Standard Electrical Dictionary. 

PRICE, $3.00. 



NORMAN W. HENLEY & CO., Publishers, 

132 Nassau Street, New York. 



THE 



STANDARD ELECTRICAL DICTIONARY 



A POPULAR DICTIONARY OF WORDS, TERMS, 

AND PHRASES, USED IN THE PRACTICE 

OF ELECTRICAL ENGINEERING. 



A Concise and Practical Book of Reference. 



SECOND EDITION, REVISED, AND ENLARGED 

By ax appendix, Bringing the work uv po 
i hk Present Time. 



By T. O'CONOR SLOANE, A.M., E.M., Ph.D., 

Author of 
" Arithmetic of Electricity,' " Electricity Simplified/' 
" Electric Toy 




\<MS ■ ' 



Nkyv York : 
NORMAN \V. HENLEY & CO. 

97 



c^i'b 



$w 



v 



Copyrighted 
r>\ Norman \v. hi.ni. iv ft Co. 

Copyrighted 1897, 

BY Norman W. Hi.m.i.y & G<>. 



PREFACE. 

The purpose o( this work is to present the public with a concise 
and practical book of reference, which it is believed will be appre- 
ciated in this age of electricity. The science has expanded so 
much that the limits of what may be termed strictly a dictionary 
of the present day would a few years ago have sufficed for an ency- 
clopedia. It follows that an encyclopedia of electricity would be a 
work of great size. Yet a dictionary with adequate definitions, 
and kept within the closest limits by the statement of syno- 
nyms, and by the consigning of all the innumerable cross-references 
to a concise index will be far more than a mere dictionary in the 
ordinary sense of the term. 

Duplication of matter is to be avoided. This makes many defi- 
nitions appear short. Yet, by the assistance of the reader's own 
general knowledge, and by referring to the very complete index, 
almost any subject can be found treated in all its aspects. 

There are exceptions to this statement. So much has been done 
in the way of mechanical detail, so many inventions in telegraphy 
and other branches have sprung into prominence only to disappear 
again, or to be modified out of recognition, that to embody descrip- 
tions of many ingenious and complicated apparatus has been abso- 
lutely impossible for want of space. 

A word as to the use of the book and the system of its construc- 
tion may be given here. Each title or subject is defined once 
in the text. Where a title is synonymous with one or more others 
the definition is only given under one title, and the others appear 
at the foot of the- article- as synonyms. It may be that the reader is 

seeking the definition of one of these synonyms. It' s<> a reference 



vi PREFACE. 

to the index shows him at once what page contains the information 
sought for. The use of an index in a work, necessarily of an ency- 
clopedic form, will be appreciated by all users of this book. 

Where a title embraces several w r ords, all orders of the word will 
be cited in the index. To make the operation of finding references 
easy this rule has been carried out very fully. 

PREFACE TO SECOND EDITION. 

Since the issue of the first edition of this work electrical science 
has advanced much in all its branches, the Electrical Congress of 
1893 has given us well-defined units, the marvellous discovery of 
Rontgen has startled the world, new applications have been made, 
new specialties invented, and so the need of an addition was clearly 
manifest. This has been done, bringing the work up to the present 
date. 

September, 1S97. Tin-: AUTHOR. 

SYMBOLS AND ABBREVIATIONS. 
adj. Adjective. 
v. Verb. 
q. v. il Which see." 

/ A mark of division, A B, meaning "A divided by B." 
— '— The same as above. 

= A mark of equality, meaning •• is equal to." 
X A mark of multiplication, meaning " multiplied by." 
Fractional exponents indicate the roots expressed by their demon- 
inators and the powers expressed by their numerators. Thus, A 
means the " square root of A ;" A 3 means the " cube root of A ;" 
B2 means the " square root of the cube or third power of B." 

The use of powers often, as io 10 , io 11 , as multipliers, will be found 
explained at length in the definition Tdi, Powers of, 



STANDARD 
ELECTRICAL DICTIONARY, 



A. Abbreviation for anode, employed in text relating to electro- 
therapeutics. It is sometimes written An. 

Abscissa. In a system of plane eo-ordinatcs see Co-ordinates) 

Y 



o 



Fig. 



AXKS OF G KORDI1 



■:iv point from the axis of ordinate s measured par- 
allel to the axis 

In the cut the f the point a is the line «»r distance a 

Absolute, adj. in quantities it may he defined :i< referring 

f quantity, antf it is opposed t<> M relative." which 

mereb the relation of several th ch other. Thus 



8 STANDARD ELECTRICAL DICTIONARY. 

the relative resistance of one wire may be n times that of another ; 
its absolute resistance might be 5 ohms, when the absolute resist- 
ance of the second wire would be $/n ohms. A galvanometer gives 
absolute readings if it is graduated to read dircetl v amperes or volts; 
if not so graduated, it may by calibration q. v. be made to do prac- 
tically the same thing. 

Absolute Measurement. Measurement based upon the centi- 
meter, gram, and second. (See Centimeter- Gram Second 

System.) 

Absolute Temperature. Temperature reckoned from absolute 

zero (see Zero, Absolute). It is obtained by adding for the centi- 
grade scale 273, and for the Fahrenheit scale 459, to the degree 
readings of the regular scale. 

Absorption, Electric. A property of the static charge. When 
a Leyden jar is being charged it dilates a little and the capacity 
increases, so that it can take a little more charge for a given poten- 
tial difference existing between its two coatings. This phenomenon 
occurs with other static condensers, varying in degree with the di- 
electric. With shellac, paraffin, sulphur and resin, for instance, the 
absorption is very slight ; with gntta-percha, stearine, and glass, the 
absorption is relatively great. The- term is due to Faraday. Ice- 
land spar seems almost or quite destitute of electric absorption. 

A. C. C. Symbol of or abbreviation for anodic closure con trac- 
tion q. v. 

Acceleration. The rate of change of velocity. If of increase of 
velocity it is positive ; if of decrease, it is negative. It can only be 
brought about by the exercise of force and is used as the measure of 
or as determining the unit of force. It is equal to velocity I. T 
imparted, divided by time (T^ ; its dimensions therefore are L/T 2 . 
The c. g. s. unit of acceleration is one centimes r in one second. 

Accumulator, (a) A term sometimes applied to the secondary 
or storage battery. (See Battery, Secondary, 

(b) Sec Accumulator, Electro static 

(c) See Accumulator, Water Dropping. 

(d) vSce Wheel, Barlow's 

Accumulator, Electrostatic. Two conducting surfaces oppo- 
sitely placed, and separated by a dielectric, and arranged for the 
opposite charging of the two surfaces, constitute an accumulator, 
sometimes termed a condenser. As this arrangement introduces 
the clement of a bound and of a binding charge, the electrostatic 
capacity of such is greater than that of either or of both of its com- 



STANDARD ELECTRICAL DICTIONARY. 9 

ponent surfaces. The thinner the dielectric which separated the 
conducting surfaces, and the larger the surfaces the greater is the 
capacity ; or the less will be the potential difference which a given 
charge will establish between its two coatings. The nature of the 




Fig. 2. Sir William Thomson's Watbr-DroppinC Accumulator. 



dielectric also determines its capacity. 

Inductive.) 



See ( dpaci/y, Specific 



Accumulator, Water Dropping:. This is also known as Sir 
William Thomson's Water-Gravity Electric Machine. It is an ap- 
paratus for converting the potential energy of falling water drops, 
due to gravity, into electric energy. Referring to the illustration, 
G represents a bifurcated water pipe whose two faucets are adjusted 
to permit a series of drops to fall from each, ('and Fare two 
metallic tubes connected by a conductor ; E and Dare the same. 
Two Leyden jars, A and B y have their inner costings represented by 
sulphuric acid, connected each to its own pair of cylinders, 
ad i / to F and ( ". The outer coatings are connected 
the water supply. One of th . f, is 

rilywithpo ctricity. This charge, e'and/-, 

with it, being in electric rith. Just before the 

the jet leading into C, they are inductively 



io STANDARD ELECTRICAL DICTIONARY. 

charged with negative electricity, the positive going to earth. Thus 
a series of negatively excited drops fall into the metal tube D, with 
its interior funnel or drop arrester, charging it, the Leyden jar B t 
and the tube E with negative electricity. This excitation causes 
the other stream of drops to work in the converse way, raising the 
positive potential of F and C and A, thus causing the left-hand 
drops to acquire a higher potential. This again raises the potential 
of the right-hand drops, so that a constant accumulating action is 
kept up. The outer coatings of the Leyden jars are connected to 
earth to make it possible to raise the potential of their inner coat- 
ings. In each case the drops are drawn by gravity into contact 
with objects similarly excited in opposition to the electric repul- 
sion. This overcoming of the electric repulsion is the work done 
by gravity, and which results in the development of electric energy. 

Acidometer. A hydrometer or areometer used to determine the 
specific gravity of acid. They are employed in running storage 
batteries, to determine when the charging is completed. | Sec Are- 
ometer.} 

Aclinic Line. A terrestrial element; the locus on the earth's 
surface of no inclination of the magnetic needle ; the magnetic 
equator. (See Magnetic Elements* I 

Acoustic Telegraphy. The system of sound-reading in teleg- 
raphy, universally used in the Morse system. The direct stroke of 
the armature of the electro-magnet and its " back stroke " disclose 
to the ear the long and short strokes, dots and lines, and long and 
short spaces as produced by the dispatcher of the message. In the 
Morse system a special magnet and armature is used to produce the 
sound called the "sounder;" in other systems, e. g., Steinhcil's 
and Bright's apparatus, bells are used. (See Alphabets s Tele- 
graphic.) 

Acoutemeter. A Hughes audiometer or sonometer applied to 
determining the quality of a person's hearing (See Hughes' Induc- 
tion Balance, — Audiometer). The central coil by means of a tuning 
fork and microphone with battery receives a rapidly varying cur- 
rent tending to induce currents in the other two coils. Telephones 
are put in circuit with the latter and pick up sound from them. 
The telephones are applied to the ears of the person whose hearing 
is to be tested. By sliding the outer coils back and forth the 
intensity of induction and consequent loudness of the sounds in the 
telephones is varied. The position when the sounds grow so faint 
as to be no longer audible, gives the degree of delicacy of the per- 
son's hearing. By using a single telephone the same apparatus 
affords a means of testing the relative capacity of the right and left 



STANDARD ELECTRICAL DICTIONARY. u 

Actinic Rays. The rays of light at the violet end of the 
spectrum ; also the invisible rays beyond such end, or the cihcr 
waves of short periods which most strongly induce chemical 

change. 

Actinism. The power possessed by ether waves of inducing 
chemical change, cither of decomposition or of combination. The 
violet and ultra-violet end of the spectrum of white light, generally 
speaking, represent the most highly actinic rays. 

Actinometer, Electric. Properly an apparatus for measuring 
the intensity of light by its action upon the resistance of selenium. 
A current produced by fixed electro-motive force passing through 
the selenium affects a galvanometer more or less according to the 
intensity of the light. It is more properly an electric photometer. 
The term has also been applied to a combination of a thermo-elec- 
tric pile and galvanometer, the light falling on the pile affecting 
the motions of the galvanometer. 

Action, Local, (a) The wasteful oxydation of the zinc in a 
galvanic battery due to local impurities and variations in the com- 
position of the zinc. These act to constitute local galvanic couples 
which cause the zinc to dissolve or oxydize, without any useful 
result. Amalgamation of the zinc prevents local action. Chemic- 
ally pure zinc is also exempt from local action, and can be used in 
an acid battery without amalgamation. (See Amalgamatioti .) 

id) The same term has been employed to indicate the eddy or 
foucault currents in dynamo electric machines. (See 
Cu rrcn t , Fo uca ult.) 

Activity. The rate of doing work ; the work done per second 

by any expenditure of energy. The activity of a horse-power is 

550 foot lbs. per second, or 746 volt-coulombs per second. The 

practical electric unit is the volt-ampere, often called the watt. 

Sec Energy, Electric.) 

Adapter. A screw coupling to engage with a different sized 
screw on each end ; one of the uses is to connect incandescent lamps 
to gas- fixtures. 

A. D. C. Abbreviation for Anodic Duration Contraction , q. v.; 
a term in electro-therapeutics. 

Adherence, Electro-magnetic. The adherence between sur- 
faces of iron due to electro-magnetic attraction. It has been 
applied to the driving-wheels of an engine and rail, whose grip is 
increased by such action. In one method a deep groove was cut 
around the wheel which was wound with a magnetizing coil. Thus 
one rim becomes a north and the other a south polo, and the rail 
completing the circuit acts as the armature. Such an arrangement 



12 



STANDARD ELECTRICAL DICTIONARY. 



prevents a wheel from sliding. Electro-magnetic adherence has 
also been employed to drive friction gear wheels. In one arrange- 




Fig. 



3. Electro-magnetic 
Car Wheel. 




Electro-magnetic Friction 



ment the two wheels arc surrounded by a magnetizing coil, under 
whose induction each attracts the other, developing high adherence 
between their peripheries. 

Admiralty Rule of Heating. The British Admiralty specifica- 
tions for the permissible heating of dynamos. It holds that at the 
end of a run of six hours no part of the dynamo under trial shall 
show a rise of temperature greater than n° C. (20 F.) above the 
temperature of the air surrounding it. This is thought to be a very 
stringent and unnecessarily high requirement. 

Aerial Conductor. An electric conductor carried from house- 
tops, poles, or otherwise so as to be suspended in the air, as dis- 
tinguished from an underground or submarine conductor. 

Affinity. The attraction of atoms and in some cases perhaps of 
molecules for each other by the force of chemical attraction. 
When the affinity is allowed to act or is carried out, a chemi- 
cal change, as distinguished from a physical or mechanical 
change, ensues. Thus if sulphur and iron are each finely powdered 
and are mixed the change and mixture are mechanical. If slightly 
heated the sulphur will melt, which is a physical change. If heated 
to redness the iron will combine with the sulphur forming a new 
substance, ferric sulphide, of new properties, and especially charac- 



STANDARD ELECTRICAL DICTIONARY. 13 

tcri/cd by unvarying and invariable ratios of sulphur to iron. 
Such change is a chemical one, LS due to chemical affinity, 19 due 

to a combination of the atoms, and the product is a chemical com- 
pound. 

Agir Motor. The Anderson and (Tirdlcstone motor. The term 
11 agir" is made up from the first portions of each name. 

Agonic Line. The locus of points on the earth's surface where 
the magnetic needle points to the true north ; an imaginary line 
determined by connecting points on the earth's surface where the 
needle lies in the true geographical meridian. Such a line at pres- 
ent, starting from the north pole goes through the west of Hud- 
son's Ray, leaves the east coast of America near Philadelphia, 
passes along the eastern West Indies, cuts off the eastern projection 
of Brazil and goes through the South Atlantic to the south pole. 
Thence it passes through the west of Australia, the Indian Ocean, 
Arabia, the Caspian sea, Russia and the White sea to the North 
Pole. It crosses the equator at 70 W. and 55 E. approximately. 
See Magnetic Elements,) 

Synonym — Agone. 

Air. Air is a dielectric whose specific inductive capacity at at- 
mosphere pressure is taken as 1. It is practically of exactly the 
same composition in all places and hence can be taken as a stand- 
ard. When dry it has high resistance, between that of caout- 
chouc and dry paper. Dampness increases its conductivity. 

It is a mixture of oxygen and nitrogen, with a little carbonic 
acid gas and other impurities. Its essential composition is : 

Oxygen: t^by weight) 23.14 (by volume) 21 
Nitrogen : 76.86 79 

The specific inductive capacity varies for different pressures thus : 

Approximate vacuum (.001 mm., .0004 inch) 0.94 (Ayrton) 

11 " (5 mm. 2.0 inches) - 99 5 

' (0.99941 (Boltzman. 1 

The specific gravity of air under standard conditions 15. 5 C 
(6o° F.i and 760 mm. barometric pressure (30 inches) is taken as 
unity as a standard for gases. 

Air-BIast. [a) In the Thomson-Houston dynamo an air-blast 

I to blow away the arc-producing spark liable to form between 

the brashes and commutator. It is the invention of Prof. Klihu 

Thomson. The arc is supplied by a positive action rotary blower 

connected to the main shaft,, and driven thereby. The wearing of 

the commutator by destructive sparking is thus prevented. 



14 



STANDARD ELECTRICAL DICTIONARY. 



A drum H H \s rotated, being mounted on the axis X of the 
dynamo. As it rotates the three vanes are thrown out against the 
irregular shaped periphery of 
the outer case T T. The arrow 
shows the direction of rota- 
tion. The air is thus sent out 
by the apertures a a. O is the 
oil-cup. 

(6) The air-blast has also been 
used by Prof. Thomson in 
experiments with high fre- 
quency currents of high poten- 
tial. By directing a blast of 
air against a spark discharge 
between ball terminals of an 
alternating current, the nature 
of the current was changed and 
it became capable of producing 
most extraordinary effects by 
induction. Fig. 5. Air Blowrr for Thomson's 

Dynamo. 




Air Condenser. A static condenser whose dielectric is air. 
The capacity of an air condenser in farads is equal to 



4.452 X io 1 -' X / 



in which A is the area of one sheet or sum of the areas of one set of 
connected sheets in square inches and / is the thickness of the Layer 
of air separating them. 

A convenient construction given by Ayrton consists in a pile of 
glass plates /^separated by little bits of glass Foi known thickness, 
three for each piece. Tin-foil T^is pasted on both sides of each piece 
of glass and the two coatings are connected. The tin-foil on each 
second plate is smaller in area than that on the others. The plates 
are connected in two sets, each set comprising every second plate. 
For A in the formula the area of the set of smaller sheets of tin-foil 
is taken. By this construction it will be seen that the glass does 
not act as the dielectric, but only as a plane surface for attachment 
ofthe tin-foil. Posts E E keep all in position. One set of sheets 
connects with the binding post A, the other with B. 

The capacity of any condenser with a dielectric of specific in- 
ductive capacity i is given by the formula : 



% X 



A 1 



4.452X 10" X t x 



STANDARD ELECTRICAL DICTIONARY. 



15 




Air Condenser. 

The air condenser is used for determining the value of i for differ- 
ent dielectrics. 

Air Gaps. In a dynamo or motor the space intervening be- 
tween the poles of the field magnet and the armature. They should 
be of as small thickness, and of as extended area as possible. Their 
effect is to increase the magnetic reluctance of the circuit, thereby 
exacting the expenditure of more energy upon the field. They also, 
by crowding back the potential difference of the two limbs, increase 
the leakage of lines of force from limb to limb of the magnet. 

Air Line Wire. In telegraphy the portion of the line wire 
which is strung on poles and carried through the air. 

Air Pump, heated. It has been proposed to heat portions of 

a mercurial air pomp to secure more perfect vacua, or to hasten the 
action. Heating expands the air and thus produces the above 
effct 



16 STANDARD ELECTRICAL DICTIONARY. 

Air Pump, Mercurial. An air pump operated by mercury. 
The mercury acts virtually as the piston, and the actuating force is 
the weight of the column of mercury, which must exceed thirty 
inches in height. There are many types. Mercurial air pumps 
are largely used for exhausting incandescent lamp chambers. 
Geissler Air Pump, — Sprengel Air Pump.) 

Air Pumps, Short Fall. A mercurial air pump in which the 
fall of mercury or the height of the active column is comparatively 
small. It is effected by using several columns, one acting after the 
other. A height of ten inches for each column suffices in some 
forms. Enough columns must be used in succession to make up 
an aggregate height exceeding 30 inches. 




Fig. 7. Burglar Alarm Switch ok Circuit Brrakrr. 

Alarm, Burglar. A svstem of circuits with alarm bell extend- 
ing over a house or apartments designed to give notice of the open- 




Fig. 8. Burglar Alarm Switch or Circuit Breaker. 



STANDARD ELECTRICAL DICTIONARY. 17 

ing of a window or door. As adjuncts to the system the treads of 




Burglar Alarm Switch or Circuit Breaker. 



the stairs are sometimes arranged to ring the bell, by completing a 
circuit when trod on. Door mats arc also arranged to close ch- 
cuits in like manner. 

For doors and windows switches are provided which are open as 
long as the door or window is closed, but which, on being released 
by opening the door or windows, automatically close the circuit. 
The circuit includes an alarm bell and battery, and the latter be- 
gins to ring and continues until stopped, either by the closing of 
the door or by a switch being turned. The connections are some- 
times so contrived that the reclosing of the door or window will 
not stop the bell from ringing. 

The cuts show various switches for attachment to doors and win- 
dows. It will be seen that they normally keep the circuit closed, 
and that it is only open when pressure, as from a closed door, is 
brought upon them. In the case of a door a usual place for them 
is upon the jamb on the hinge side, where they arc set into the 
wood, with the striking pin projecting, so that as the door is closed 
the pin is pressed in, thus breaking the circuit. 

Sometimes the connections are arranged so as to switch on the 
electric lights if the house is entered. Special annunciators show- 
ing where the house has been entered are a part of the system. A 
clock which turns the alarm on and off at predetermined hours is 
also sometimes used. 

The circuits may be carried to a central station or police station. 

One form of burglar alarm device is the Vale lock switch. This 
is a contact attached to a Yale lock which will hr closed if the 
g key is used, completing a circuit and ringing a bell. 

Alarm, Electric. An appliance for calling attention, generally 
by ringing a bell. It is used to notify of water-level in boi] 

atrance of a house, or of other tlii:. sired, it is 

evident that any number of alarms could be contrived. 

Alarm, Fire and Heat. An alarm for giving notice <»f the 

nee of a conflagration. Such are sometimes operated by a 



i8 STANDARD ELECTRICAL DICTIONARY. 

compound bar thermostat (see Thermostat), which on a given 
elevation of temperature closes a circuit and rings an electric bell. 
Sometimes the expansion of a column of mercury when heated is 
used. This, by coming in contact with one or two platinum points, 
completes a circuit, and rings the bell. 

The identical apparatus may be used in living rooms, green- 
houses, factories and elsewhere, to give an alarm when the tempera- 
ture rises or falls beyond predetermined limits. 

Alarm, Overflow. An alarm to indicate an overflow of water 
has been suggested on the lines of a contact completed by water, or 
of the elements of a battery which would be made active by water. 
Thus two sheets of metal might be separated by bibulous paper 
charged with salt. If these sheets were terminals of a circuit in- 
cluding a bell and battery, when water reached them the circuit 
would be closed and the bell would ring. It was also proposed to 
use one copper and one zinc sheet so as to constitute a battery in 
itself, to be thrown into action by moisture. These contacts or in- 
active batteries could be distributed where water from an overflow 
would be most likely to reach them. 

Alarm, Water Level. An alarm operated by a change of water 
level in a tank or boiler. By a float a contact is made- as it : 
with the water. Another float may be arranged to Jail and close a 
contact as the level falls, 'flic- closing of the contacts ring., an elec- 
tric bell to notify the attendant in charge. 

Alcohol, Electrical Rectification of. A current of electricity 
passed through impure alcohol between zinc electrodes is found to 
improve its quality. This it does by decomposing the water pres- 
ent. The nascent hydrogen combines with the aldehydes, convert- 
ing them into alcohols while the oxygen combines with the zinc 
electrode. 

Alignment. The placing in or occupying of the same straight 

line. The bearings of a shaft in dynamos, engines, and other 
machinery have to be in accurate alignment. 

Allotropy. The power of existing in several modifications 
possessed by some substances, notably by chemical elements. In- 
stances of the allotropic state are found in carbon which exist- 
charcoal, as graphite (plumbago or black lead), and as the diamond. 
All three are the same elemental substance, although differing in 
every physical and electrical property. 

Alloy. A mixture, produced almost universally by fusion, of 
two or more metals. Sometimes alloys seem to be chemical com- 
pounds, as shown by their having generally a melting point lower 
than the average of those of their constituents. An alloy of a metal 
with mercury is termed an amalgam. An important application 



STANDARD ELECTRICAL DICTIONARY. 19 

in electricity is the use of fusible alloys for lire alarms or for safety 
fuses. German silver is also o{ importance for resistance coils, 
and palladium alloys are used for unmagncti/.ablc watches. An al- 
lov of wrought iron with manganese is almost unmagncti/.ablc, 
and has been proposed for use in ship building to avoid errors of 
the compass. 

Alloys or what are practically such can be deposited by elec- 
trolysis in the electro-plater's bath. We give the composition of 
some alloys interesting to the electrician. 

Solder: Lead 1 part Tin 2 parts 



German Silver : Copper, 2 parts ; Nickel, 1 part; Zinc, 1 part 
(used for resistances). See page 277. 

'Platinum-silver Alloy : Platinum, 1 part ; silver, 2 parts (used for 
resistances). See page 419. 

Palladium alloys for watch springs. (^Sec Palladium.) 



Alphabet, Telegraphic. The combinations of sounds, of dots 
and dashes marked on paper, of right-hand and left-hand deflec- 
tions of a needle, of bells of different notes, or of other symbols by 
which a fixed combination is expressed for each character of the 
alphabet, for numerals, and for punctuation. While the code is 
designed for telegraphic uses it can be used not only for the con- 
veyance of signals and messages by the electrical telegraphs, but 
also by any semaphoric or visual system, as by flashes of light, 
movements of a flag or even of the arms of the person signalling. 

In the English and continental needle telegraphy in which the mes- 
sage is transmitted by the movements of an index normally verti- 
cal, but oscillating to one side or the other under the influence of 
the current, the latter being controlled bv the transmitter of the 
message, the left hand swings of the needle are interpreted as dots, 
the right hand as dashes. 

This system enables one alphabet to be translated into the 
other, or virtually one alphabet answers for both Morse and needle 

transmitt 

There are two principal telegraphic alphabets, the American 

and the International codes. They arc very similar, their 
rial distinction being that spaces arc- used in the American 
while they are excluded from the- International code. 

In the American Morse system the message IS now universally 
received by sound. (See Sounder— Sound Reading.) 



20 STANDARD ELECTRICAL DICTIONARY. 

The two codes or telegraphic alphabets are given here. 

THE INTERNATIONAL ALPHABET. 





Parenthesis, 








Understand, 















Wait, 









Erase, 














Call signal, 








End of message, 








Cleared out all r 


i ,r ht 




A 
B 
C 
D 
E 
F 
G 
H 
I 


L 

M 

N 



p 

Q 

R 

vS 

T — 


W 

X 

Y 

Z 

Ch 

A 



u 








J 





U 


E 


K 




V 

% NUMERALS. 


N 


I 




4 


8 


2 




5 


9 


3 




6 


o 






7 






STANDARD ELECTRICAL DICTIONARY. 

PUNCTUATION, ETC., 
Period (.) 

Comma . 

Query(?) 

Exclamation 

Apostrophe ( ' ) 

Hyphen (-) 

Fresh paragraph, 

Inverted commas, 

THE AMERICAN ALPHABET. 

A J S - 

B K T - 

C L U - 

D M V - - 

E - N W - - 

F 0-- X -- 

G P Y- 

H --- Q Z -- 

I-- R & - 

i 4 8 — 

2 5 9 _ 

3 6 o — 



Comma (,) 
vSemicolon (;) 
Colon (:) 
Colon Dash (:— ) 
Period (.) 
Interrogation (?) 
Exclamation 
Dash (— ) 
Hyphen (-) 
Pound Sterling 
Shilling Mark 



22 STANDARD ELECTRICAL DICTIONARY. 

Dollars ($) Decimal Point (.) — 

Cents (c) Paragraph (f) 

Pence (d.) Fractional Mark { ) 

Capitalized Letter — 

Italics or Underline 

Colon followed by (Quotation : 4 ' 

Parenthesis ( ) 

Brackets [ ] 

Quotation Marks " " 

Quotation within a Quotation H ' ' " 

The principal differences in the two codes are the nse of 
in the American code, such being excluded from the Interna- 
tional code. This affects the Letters C, R, Y, & Z. 

The following diagram, due to Commandant Perian, enables the 
letter corresponding to an [nternationa] code sign to be rapidly 

found with the exception of R. 



./ 




K 



/\ /\, /\ /\ 

A A AA a a a a 

*l VF U U AP J B XC Y 2 QOCN 

Fig. 10. Diagram for translating the Morse Alphabet. 

In order to find what letter corresponds to a given sign, starting 
from the top of the diagram, each line is traced down to a bifur- 
cation, taking the right hand line of each bifurcation for a dash, 



STANDARD ELECTRICAL DICTIONARY. 23 

and the left hand line for a (A'/, and stopping when the dots and 

dashes are used up. Thus, for example, the signal leads us 

to the letter </. the signal to the letter / and so on. 

Alternating. adj. Term descriptive of a current changing 
periodically in direction. (See Current, Alternating.) 

Synonyms — Oscillatory — periodic — undulatory — harmonic. 

Alternating Current Arc. The arc produced by the alternating 

current. It presents several peculiarities. With an insufficient 

number of alternations per second it goes out. As the carbons 
wear away equally it is adopted for such lamps as the Jablochkoff 
candle, i^see Candle \Jablochkoff). As no crater is formed the light 
is disseminated equally both up and down. For this reason to 
get full downward illumination a reflector is recommended. 

Alternating Current System. A system of electric distribu- 
tion employing the alternating current. For transmission in the 
open air or in conduits a high potential circuit is used, from 1,000 to 
10,000 volts being maintained at the central station. Two leads un- 
connected at the end lead from the station. Where current is desired 
a converter or transformer (see Converter) is placed, whose primary- 
is connected to the two leads bridging the interval between them. 
From the secondary the house leads are taken with an initial 
potential in some cases of 50 volts. The converters are thus 
all placed in parallel. By law or insurance rules the con- 
verters are generally kept outside of buildings. Where no 
secondary current is taken from the converters very little 
primary current passes them on account of their counter-electro- 
motive force. As more secondary current is taken the primary in- 
creases and this accommodation of one to the other is one of the 
interesting and valuable features. Street lamps are sometimes con- 
nected in series. Each lamp in such case is in parallel with a 
small coil with iron core. While the lamp is intact little current 
passes through the coil. If the lamp is broken, then the con- 
verter impedes the current by its spurious resistance, q. v., just 
enough to represent and replace the resistance of the extinguished 
and broken lamp filament (Sec Meter, Alternating Current ; 
Motor, Alternating Current. 

Alternation. The change in direction of a current. The num- 
ber of Mich changes is expressed as number of alternations ; thus a 
current may have a frequency of 500 or 20,000 alternations per 
id. 

Alternation, Complete. A double alternation ; a change from 
one direction to the other and bark again to the original ph.e 
symbol derived from it^ graphic representation by a sine curve 
sed to indicate it. The symbol is ■*■ 



24 STANDARD ELECTRICAL DICTIONARY. 

Alternative Path. A second path for a current appearing as a 
disruptive discharge. Where two paths are offered the discharge, 
as it is of alternating or oscillatory type, selects the path of least 
self-induction. Thus a thick bar of copper, with no air gap, may 
be abandoned by the current in favor of a small iron wire with an 
air gap, but which has less self-induction. 

The lightning arresters, q. v., for the protection of telegraph offices 
are sometimes based on these principles. A path of very high re- 
sistance but of small self-induction is offered between the line and 
the earth. This the lightning discharge selects in preference to the 
instruments with their iron cores, as the latter are of very high self- 
induction. 

Alternator. A dynamo electric generator supplying an alter- 
nating current. (See Dynamo, < XUernaiing ( urrenL I 
Synonym — Alternating current generator or dynamo. 

Alternator, Constant Current. An alternating current dynamo 
supplying a current of unvarying virtual amperage. Alternators ^f 
this type are constructed with an armature of high self-induction. 

Sometimes fine winding contained in deep peripheral notches in the 
core-discs is employed to magnify the- self-induction. Such gener- 
ators are employed for series lighting, especially arc-lighting. 

Aluminum. A metal; one of the elements; symbol: Al. 
Atomic weight: 27.4. Equivalent: 0.13. Valency: 3. Specific 
gravity: 2.6. It is a conductor of electricity. 
Relative resistance annealed, (Silver 1 1. 

Specific resistance at at o°C. microhms 

Resistance of a wire at 0°C. (32 P.) 

(a) 1 foot long, weighing 1 grain, 0.1074 ohms. 

(6) I foot long, 1 IOOO inch thick, 17-53 

(r) 1 meter long, weighing 1 gram, 0.0749 
(a) 1 meter long, I millimeter thick 0.03710 

Resistance of a I-inch cube at o°C. (32°F.) 1.147 microhms 
Blectro-chcmical equivalent. .095S (hydrogen -0105) 

Amalgam, (a) A combination or alloy in which one of the 
constituents is mercury. Usually the term is applied to an alloy of 
a single metal with mercury. Some metals readily form amalgams; 
such metals are : Gold, zinc, silver, lead and others ; some, such as 
platinum and iron, form amalgams only under exceptional circum- 
stances. 

(6) The word is also applied to compositions for application to 
the cushions of frictional electric machine in which cases it is often 
a misnomer. True amalgams used for this purpose arc made as 
follows : 



STANDARD ELECTRICAL DICTIONARY. 25 

(a) Tin, 1 part; Zinc, 1 pan; Mercury, 2 parts [Kienmayer . 
\b^ Tin, 2 parts ; Zinc, 3 parts. 
[c] Tin, 3 parts ; Zinc, 5 parts : Mercury, 9 parts. 
Zinc, 1 part ; Mercury, 4 parts 

The tin, if such is nscd, (formula <7, 6 and c) is first melted, trie 
zinc is added in successive portions. The mercury, which must be 
heated, is slowly poured into the melted alloy after removal of the 
latter from the tire, and the mixture, while making, is constantly 
stirred. It is kept stirred or rubbed in a mortar until cold. Some- 
times it is poured into water and kept in constant agitation until 
cold. It is thus obtained in a granular condition, and is pounded 
in a mortar until reduced to powder. It must be dried and kept 
in tightly stopped bottles and is applied to the cushions after they 
have been greased. It is to be noticed that it is said that alloy (d) 
requires no pulverization beyond constant rubbing in a mortar as 
it cools. Sometimes the amalgam is shaken about in a wooden tray 
with chalk while cooling. The action of amalgams is not very 
clearlv understood. Some claim that there is a chemical action, 
others that they simply act as conductors, others that they are more 
highly negative to the glass than the leather of the cushions. 

Graphite or sulphide of tin (mosaic gold) are sometimes used to 
coat the cushions ; it is these that are sometimes incorrectly 
called amalgams. 

Amalgamation, the application of mercury to a metal with which 
it forms an amalgam, or with which it amalgamates. Battery zincs 
are amalgamated in two ways. In the immersion method, the 
plate is dipped into an acid solution of mercuric chloride or nitrate. 
The latter is best. In the direct application method the plate is 
first wet all over with dilute acid and a little mercury is dropped 
upon it and is rubbed over the surface with a rag or, what is better, 
with a piece of galvanized iron. A very little mercury answers the 
purpose. The whole surface of the plate should be left as bright as 
silver. ^See .let ion, Local.) 

Amber. Amber is a fossil resin, supposed to be a product of the 
extinct Pinites Succinifer and other coniferous trees. Most of it 
is gathered on the shores of the Baltic between Koenigsberg and 
Memel. It is also found in small pieces at (jay Head, Mass., and in 
New Jersey green sand. It is found among the prehistoric remains 
of the Swi>s Lake dwellers. When rubbed with a cloth it becomes 
excited with negative electricity. The Greek word for it is elec- 
tron, which gave the name electricity to the modern science. Thalcs 
of Miletus, 000 B. C, and TheophrastUS, about 300 I». C., both men- 
tion its electric properties or power of attracting small objects 
When rubbed. 



26 STANDARD ELECTRICAL DICTIONARY. 

Ammeter. The commercial name for an ampere-meter, an in- 
strument designed to show by direct reading the number of 
amperes of current which are passing through a circuit. 

A great variety of ammeters have been invented, based on differ- 
ent principles. The definitions following this one give some idea 
of the lines of construction followed. 

Synonym — Ampere meter. 

Ammeter, Ayrton's. A direct reading instrument for measur- 
ing current intensity. 

A solenoid receives the current. In the axis of the solenoid an 
iron tube is suspended by a long spiral spring that passes down 
within it, and the upper end of which spring is fastened to the 
glass top of the instrument. The tube is provided with proper 
guides so as to maintain a vertical position, and is free to rotate. 
Its upper end carries an index. 

The whole operates as a magnifying device. A slight longitud- 
inal displacement of the tube causes it to rotate through a consider- 
able angle by the action of the spring. By properly proportioning 
the parts, the angle of displacement of the index is directly 
proportional to the current between [5 and 270" angular displace- 
ment. 

The same instrument is wound for use R9 a volt-meter. 

Its principal fault is its restricted rang 

Ammeter, Commutator. A commutator ammeter is one 
whose windings consist of separate strands, each of any desired 
number of turns, and provided with a commntating attachment 
for throwing them into series or into parallel as desired. The 
essential condition is that all the wires shall be of equal resistance 
and of equal number of turns. Such an instrument can be used for 
heavy or light currents. Two sets of graduations are marked on 
its scale if it is a calibrated instrument. (Sec Calibration.) Com- 
mutator volt-meters are constructed on the same principle. 

Ammeter, Cunynghame's. A modification of the Siemens' 

electro-dynamometer. (Sec lilcctro-dy)iamouictc)\ Siemens'.) An 
electro-magnet with very massive core is excited by the current. 
As the core is of small reluctance the strength of the magnet is 
nearly proportional to the current strength. Between the poles of 
the magnet a soft iron armature or induced magnet is pivoted. It 
carries a pointer so adjusted that when the axis of the soft iron 
magnet is at an angle of about 30 with the line joining the poles 
of the electro-magnet the pointer will indicate zero. 

The soft iron armature is so massive that the magnetism induced 
in it is proportional to the strength of the electro-magnet. Hence 



STANDARD ELECTRICAL DICTIONARY. 



27 



the couple exerted by the electro-magnet on the pivoted armature 
will be proportional to the square of the current. 

The armature is retained in place by a spiral spring lying in line 
with its axis of rotation. The instrument is operated as a zero 
reading instrument. The current is passed through it. The needle is 
deflected; it is brought back to zero by turning a milled head which 
twists the spring. The current will be proportional to the square 
root of the angle of displacement of the milled head. A scale with 
index is provided, giving directly the square roots of the angle 
over which the pointer is moved. 

The same instrument is wound for use as a volt-meter. 

Ammeter, Eccentric Iron Disc. This ammeter comprises a 
cylindrical electro-magnet excited by the current to be measured. A 
disc of iron free to rotate is suspended on pivots below it. A piece is 
cut off the disc at one part of its periphery so as to give more metal 
to one side than to the other. In its zero position this portion of the 
disc swings towards the magnet. As the latter is more and more 
excited the other or more projecting portion of the disc turns 
towards it, being attracted like an armature, and moves against the 
force of gravity, the disc rotating. An index attached to the disc 
swings over the face of a graduated scale. The disc is so counter- 
poised that in its natural position the index points to zero. 

Ammeter, Electro = mag= 
netic. An ammeter depend- 
ing for its working upon the 
action of an electro-magnet, 
which is excited by the current 
to be measured. 

Ammeter, Gravity. An am- 
meter whose hand or index is 
drawn into the zero position by 
gravity, and whose displacement 

therefrom is produced by the 
action of the current to be meas- 
ured. 

Ammeter, Magnetic Vane. 

A fixed plate of soft iron is placed 
within a coil. Pacing it i^ a 
Second disc free to move or swing 
on an axis. When the field is 
excited the two repel each other 

because like- polarity is Induced 
in each, and the motion of 
the movable disc indicates the 
Fig. n. Gka . trength of the current. The 




28 



STANDARD ELECTRICAL DICTIONARY. 



same instrument is wound for high resistance and constitutes a 
Magnetic Vane Voltmeter. 

Ammeter, Magnifying Spring. A solenoid ammeter in which 
a spiral spring is used to convert the longitudinal motion of the 
armature or movable core into a rotary motion (see Ammeter, 
Ayrton's) and magnify the apparent range of motion. 

Ammeter, Permanent Magnet. An ammeter with a magnetic 
field produced by a permanent magnet. 

Ammeter, Solenoid. An ammeter in which the attraction, when 
a current is passing through it, exerted by a hollow coil of wire upon 
an iron bar or tube in line with its axis, is utilized to indicate the 
strength of current. The bar is drawn into the coil to different ex- 
tents proportional to the attraction. As an example see Ammeter \ 
Ayrton's, and cut of Gravity Ammeter* 

Ammeter, Spring. An ammeter in which the part moved by 
the current is controlled or brought to the zero position by a spring. 

Ammeter, Steel Yard. A solenoid ammeter in which the sole- 
noid core is suspended vertically from the short end of a steel yard 
fitted with a sliding weight. The current passes through the sole- 




Fig. 12. Steel Yard Ammeter. 

noid coil and attracts or draws downwards the core. A sliding 
weight is moved in and out on the long steel-yard arm which is 
graduated for amperes. In use the weight is slid out until the 
arm is in equipose ; the divisions give the amperes. 



STANDARD ELECTRICAL DICTIONARY. 



29 



Ammunition Hoist, Electric. An apparatus for use on ships 
for hoisting ammunition to the guns by an electric elevator. The 
characteristic feature of it is that a constant motion of the switch 
or handle is required to keep it in action. If the operator is shot 
so as to be incapacitated from taking charge of the switch, the 
•hoist stops until another is assigned to it. 

Amperage. Current intensity expressed in amperes, as an am- 
perage often amperes. 

Ampere. The practical unit of electric current strength. It is 
the measure of the current produced by an electro-motive force of 
one volt through a resistance of one ohm. In electric quantity it is 
the rate of one coulomb per second. It is one-tenth the absolute 
C. G. S. unit of current strength. Its best analogy is derived from 
water. Assuming the electric current to be represented by a cur- 
rent of water, the pressure, head, or descent producing such current 
would be the electro-motive force. The current might be measured 
in gallons (or other unit) passed per second. In the analogy these 
gallons would be coulombs. But it might be measured by reference 
to a standard stream, as for instance, the stream which would pass 




Fig. 13. The Miner's Inch as an Analogy for the Ami 

through a hole an inch square under a given head, sav six inches 
of water. This unit is the miner's inch, and is the exact analogy 
of the ampere. A current of water may flow at the rate of so many 
miner's inches, just as a current of electricity may flow at the rate 
many amperes. In neither case it will be noted is there any 
reference to time. "An ampere per second" is a redundant ex- 
pression, and means no more than " an ampere " ; an " ampere- 



3 o STANDARD ELECTRICAL DICTIONARY. 

second," on the other hand, is a conlomb. The number of coulombs 
passed per second gives the amperes of current. 
For value of ampere, see Coulomb. 

Ampere, Arc. A conductor bent into the arc of a circle, and 
employed in measuring the electric current by the electric balance. 

Ampere=currents. The currents assumed to be the cause of 
magnetism. (See Magnetism , Ampere's TTkeoryof.) 

Ampere=feet. The product of amperes of current by the length, 
in feet, of a conductor passing such current. It may be useful in 
empiric calculations of dynamo or motor construction, but is little 
used. One ampere-foot is a current of one ampere passing through 
one foot length of a conductor, or one-tenth ampere through ten 
feet, and so on. 

Ampere=hour. The quantity of electricity passed by a current 
of one ampere in one hour. It is used by electric power and light- 
ing companies as the unit of energy supplied by them, because 
they maintain a constant potential difference in their leads, so that 
only the amperes and hours need measuring or recording to give 
the energy, viz. : volt-ampere-hours. The- same unit is applied to 
batteries to indicate their potential energy, because they also arc 
assumed to be of constant voltage or electro-motive force 

Ampere=meters. The product of amperes of current by the 
length, in meters, of a conductor carrying such current. < )ne am- 
pere-meter is a current of one ampere passing through one meter of 
a conductor. 

The term must not be confused with the identically spelled Am- 
pere-meter, a synonym for Ammeter. 

Ampere=minute. The quantity of electricity passed by a current 
of one ampere in one minute ; sixty coulombs. 

Ampere Ring. A conductor forming a ring or circle used in 
electric balances for measuring currents. (Sec Balance, AmPi i 

Ampere=second. The quantity of electricity passed by a cur- 
rent of one ampere in one second ; the coulomb, q. v. 

Amperes, Lost. In a shunt or compound-wound dynamo, part 
of the total amperes of current produced in the armature coils go 
through the shunt, and hence, do not appear in the outer circuit. 
S. P. Thompson has proposed the term ' ' lost amperes ' ' for this 
portion of the current. 

Ampere's Memoria Technica. An expression of the effect of 
a current on a magnetic needle. If we imagine the observer in the 
line of the current and facing the magnetic needle, the current 
entering by his feet and leaving by his head, the north pole is 
deflected to his left. 



STANDARD ELECTRICAL DICTIONARY. 31 

Ampere=turns. The amperes of current supplied to a magnet 

coil multiplied by the number of turns the current makes in tin- 
coil. If the coil is wound two or three in parallel, the virtual turns 
by which the amperes arc multiplied arc one-half or one-third the 
actual turns of wire. 

Synonym — Ampere Windings. 

Ampere=turns, Primary. The ampere-turns in the primary 

coil of an induction coil or transformer. 

Ampere=turns, Secondary. The ampere-turns in the secondary 

coil of an induction coil or transformer. 

Amplitude of Waves. Waves are distinguished by length and 
amplitude. The latter, in the case of transverse waves, such as 
those of water and of the ether, correspond with and measure the 
height from lowest to highest point, or from valley to summit of 
the waves in question. In the case of longitudinal waves, such as 
those of the air, due to sounding bodies, the ratio of degree of rarefac- 
tion to degree of condensation existing in the system is the ampli- 
tude. The latter can be graphically represented by a sinuous line, 
such as would represent the section of a transverse wave. Ether 
waves are produced by heated bodies and by electro-magnetic 
impulses, as in the discharge of the Leyden jar. 

The amplitude of a wave, other things being equal, is the measure 
of its intensity. Thus, the louder a sound the greater is the ampli- 
tude of the system of waves to which it is due. The same applies 
to ether waves, whether they are perceived in the electro-magnetic, 
light, or heat-giving modification. As the amplitude of ether waves 
inot be accurately known, amplitude is a relative term and is not 
stated generally in any absolute unit. 

Analogous Pole. One of the elements ofapyro-electric crystal- 
line substance, such as tourmaline. When heated, such bodies 
acquire electrical properties. If of such crystalline form that they 
are differently modified at the ends of their crystalline axis, by 
hemihedral modifications, the ends may be differently affected. 
One end may show positive electricity when the temperature is ris- 
. and negative when falling. Such end is then called the 
.e. The opposite end presents, in such cases, the 
phenomena; becoming negative when the temperature is 
rising, and becoming positive when it is falling ; such end is called 
the antiloL 

Analysis. The determination of the elements of a Case. It may 
be chemical, and consist in finding what a substance consists of ; it 

mathematical, and consist in determining the unknown 

quantities in a problem; or it may belong to other branch© 

science. The term has a vc 1 Led application. Where the 



32 STANDARD ELECTRICAL DICTIONARY. 

constituents are only determined in kind it is called qualitative 
analysis ; where their quantity or percentage is ascertained it is 
called quantitative analysis. 

Analysis, Electric. Chemical analysis by electrolytic methods. 
(See Electrolytic Analysis.) 

Analyzer, Electric. An apparatus used in investigations on 
electric ether waves. It consists of a series of parallel metallic 
wires. When the electric waves have been polarized, the analyzer 
will only permit them to go through it intact, when the plane of 
vibration of the waves is parallel to its wires. 

Anelectrics. (a) Bodies which do not become electrified In- 
fraction ; a term introduced by Gilbert, now little used, as all 
bodies develop electricity under proper conditions by contact 
action ; the reverse of idioelec tries. 

(b) Also a conductor of electricity, the reverse of a dielectric, 
q. v. (See Conductor.) 

It will be seen that Gilbert's anelectrics were, after all, the same 
as the modern anelectrics, i.e., conductors. 

Anelectrotonus. A term used in medical electricity or electro- 
therapeutics to indicate the decreased functional activity induced 
in a nerve by the proximity of the anode- of an active electric cir- 
cuit completed through the nerve. The converse of Kathelectro- 

tonus. 

Angle of Declination. The angle of error of the magnetic 
needle or compass, measuring the extent of its deviation from the 
meridian in any locality. It is the angle- between the plane of the 
magnetic axis of a magnetic needle free to take- its natural position, 
and the geographical meridian, the needle being counterpoised if 
necessary, so as to liolel an absolutely horizontal position. The 
deviation is expressed as being east e>r west, referring always to the 
north pole. (See Magnetic Elements.} 

Syuonyjn — Variation of the Compass. 

Angle of the Polar Span. In a dynamo or motor the angle 
subtended by the portion of a pole piece facing the armature, such 
angle being referred to the centre of the cross-section of the arma- 
ture as its centre. 

Angular Velocity. The velocity of a body moving in a circular 
path, measured with reference to the angle it passes over in one 
second multiplied by the radius and divided by the time. A //;/// 
angle is taken (57°. 29578=57° 17' 44 // .8 nearly) such that it is sub- 
tended by a portion of the circumference equal in length to the radius. 
Hence, the circumference, which is 360°, is equal to 2 n X unit 



STANDARD ELECTRICAL DICTIONARY. 33 

angle, * being equal to 3.1416 — . Unit angular velocity is such as 
would in a circle of radius=i represent a path=l, traversed in unit 
time=I second. If the radius is r and the angle passed over is 0, 
the distance is proportional to rS ; if this distance is traversed in 
/ seconds the angular velocity is t. The angular velocity, if 
it is multiplied by r, expressing a distance, will give the linear 
velocity. The dimensions of angular velocitv are an angle (—arc 
-i radius ■ a Time = (L-^L) -r T T~ l . 

The velocity expressed by the rate of an arc of a circle of unit 
radius, which arc subtends an angle of 57° 17' . 
traversed in unit time, is unit angular velocity. 

Animal Electricity. Electricity, notably of high tension, gen- 
erated in the animal system, in the Torpedo, Gymnotus and Silurus. 
The shocks given by these fish are sometimes very severe. The 
gymnotus, or electric eel, was elaborately investigated by Faraday. 
It has the power of voluntarily effecting this discharge. There is 
undoubtedly some electricity in all animals. The contact of the 
spinal column of a recently killed frog with the lumbar muscles 
produces contraction, showing electric excitement. Currents can be 
obtained from nerve and muscle, or from muscle sides and muscle 
cut transversely, in each case one thing representing positive and 
the other negative elements of a couple. 

Angle of Inclination or Dip. The angle which the magnetic 
axis of a magnet, which magnet is free to move in the vertical 
plane of the magnetic meridian, makes with a horizontal line inter- 
secting such axis. To observe it a special instrument, the dipping 
compass, inclination compass, dipping needle, or dipping circle, as 
it is called, is used. (See Elements^ Magnetic, — Dipping Needle, — 
Compass, Inclination.) 

Angle of Lag. The angle expressing the displacement of the 
magnetic axis of the armature core of a dynamo in the direction of 
ition. (See Lag,) Lag is due to the motion of the arma- 
ture core. 

Angle of Lead. The angle expressing the displacement in the 
direction of rotation of the armature of a dynamo which has to be 
given the brushes to compensate for the lag. (Sec Lag.) This is 
positive lead. In a motor the brushes arc set the other way, giving 
a negative angle of lead or angle of negative lead. 

Anion. The electro-negative element or radical of a molecule, 
such as oxygen, chlorine or the- radical sulphion. (See Ions.) It 
is the portion which goes to the- anode, q. v., in electrolytic decom- 
position. 



34 



STANDARD ELECTRICAL DICTIONARY. 



Anisotropic, (adj.) Unequal in physical properties, as in conduc- 
tion and specific inductiye capacity, along various axes or directions. 
An anisotropic conductor is one whose conductivity varies accord- 
ing to the direction of the current, each axis of crystallization 
in a crystalline body marking a direction of different conductivity. 
An anisotropic medium is one varying in like manner with regard to 
its specific inductive capacity. In magnetism an a?i isotropic sub- 
stance is . one having different susceptibilities to magnetism in 
different directions. The term is applicable to other than electric 
or magnetic subjects. 

Synonym — JJlotropic. 

Annealing, Electric. Annealing by the heat produced by the 

passage of the electric current through the body to be annealed. 
The object is clamped or otherwise brought into a circuit, and a 
current strong enough to heat it to I to the- desired temper- 

ature is passed through it. 

Annunciator. An apparatus Tor announcing a call from any 

place to another, as from a living-room to an office ID a hotel, I X 




Fig". 14. Annunciator. 

for announcing the entering of any given room or window in a 
building protected by a burglar alarm. 

A usual system comprises for each annunciator an electro-magnet. 
Its armature is normally held away from its poles by a spring, and 
when in that position a latch connected to the armature holds a 
little shutter. When by a push-button or other device a current is 



STANDARD ELECTRICAL DICTIONARY. 



sent through a circuit which includes the electromagnet the arma- 
ture is attracted, this releases the latch and the shutter drops. In 
dropping it displays a number, letter or inscription which indicates 
the locality of the push-button or other circuit-closing device. 
Often annunciators are connected in circuit with a bell. 

Annunciator Clock. A clock operating an annunciator by 
making contact at determined times. 

Annunciator Drop. The little shutter which is dropped by 
some forms of annunciators, and whose fall discloses a number, 




Fig. 16. Annunciator Detaching Mechanism. 
character or inscription, indicating whence the call was sent. 

Annunciator, Gravity Drop. An annunciator whose opera- 
tions release shutters which fall by gravity. 

Annunciator, Needle. A needle annunciator is one whose 
indications are given by the movements of needles, of which there 
.illy a separate one for each place of calling. 

Annunciator, Swinging or Pendulum. An annunciator which 

Its indications by displacing from its vertical position a pen- 
dulum or vertically Suspended arm. 

Anodal Diffusion. A term in electro-therapeutics; the intro- 
duction of a medicine int., the animal system by using a sponge- 



36 STANDARD ELECTRICAL DICTIONARY. 

anode saturated with the solution of the drug in question. On 
passing a current the desired result is secured by cataphoresis, q. v. 

Anode. The positive terminal in a broken metallic or true con- 
ducting circuit ; the terminal connected to the carbon plate of a 
galvanic battery or to its equivalent in case of any other generator. 
In general practice it is restricted to the positive terminal in a 
decomposition or electrolytic cell, such as the nickel anode in a 
nickel-plating bath or the anode of platinum in a gas voltameter. 
It is the terminal out of or from which the current is supposed to 
flow through the decomposition cell. In electro-therapeutics the 
term is used simply to indicate the positive terminal. In an electro- 
lytic cell the electro-negative substance or anion goes to the anode. 
Hence, it is the one dissolved, if either arc attacked. The nickel, 
copper or silver anodes of the elcctroplatcr dissolve in use and 
keep up the strength of the bath. The platinum anode in a gat 
voltameter is uuattacked because the anion cannot act upon it 
chemically. 

Anodic Closure Contraction. A physiological change in a 
living subject produced by the dosing of the electric current; the 
muscular contraction which takes place beneath the anode applied 
to the surface of the body when the circuit is closed, the kathode 
being applied elsewhere ; it is due, presumably, to direct action on 
the motor nerve. It is a term in electro-therapeutics. It is the 
converse of anodic opening contraction^ q. v. An abbreviation 
A. C. C. is often used to designate it. 

Anodic Duration Contraction. A term in electro-therapeutics. 
On the opening or closing of an electric circuit, the anode of which 
is placed over a muscle, a contraction is observed (sec Anodic 
Closure Contraction — Anodic Opening Contraction). The above 
term is used to designate the duration of such contraction. An 
abbreviation A. D. C. is often used to designate it. 

Anodic Opening Contraction. The converse of Anodic Closure 
Contraction , q. v.; it is the contraction of living muscle beneath 
or near the anode when the circuit, including such anode and the 
body in its course, isopencdja physiological phenomenon observed 
in electro-therapeutics to which branch of science the term belongs. 
An abbreviation A. O. C. is often used to designate it. 

Anodic Reactions. A term in electro-therapeutics; the diag- 
nosis of disease by the actions of the tissue near the anode of a 
circuit. 

Anti=induction Conductor. A conductor constructed to avoid 
induction effects in the conducting element. Many kinds have 
been made. A tubular metal shield or envelope which may be 
grounded will protect an enclosed conductor to some extent. Or 



STANDARD ELECTRICAL DICTIONARY. 37 

the conductor may be a double wire twisted around itself, one 

branch being used for the regular and the other for the return 
circuit, thus constituting a closed metallic circuit. The inductive 
effects arc due to interrupted or varying currents in neighboring 

wires and circuits. Many anti-induction conductors have been 
invented and patented. 

Anti=mag;netic Shield. In general terms a hollow screen of 
soft iron designed to protect any mass of steel behind or enclosed by 
it from magnetization by any magnet near it, such as a dynamo 
field magnet. This it does by concentrating the lines of force 
within its own mass, so that "the space within it or enclosed by it 
is comparatively free from lines of force. It is often applied to 
watches, and is virtually an iron case in which they are enclosed. 

Antimony. A metal, one of the elements, atomic weight, 122 ; 
equivalent, 40.6 and 24.4; valency, 3 and 5 ; specific gravity, 6.8. 
It is a conductor of electricity. 

Relative resistance, compressed (silvcr=i\ 23.60 

Specific resistance, - - - 35-5o microhms. 

Resistance of a wire, 

1 foot long, weighing 1 grain, - - 3.41S ohms. 

1 foot long, 1- 1 000 inch thick, - 213.6 u 

(c) 1 meter long, weighing 1 gram, - - 2.3S4 " 

(d) 1 meter long, 1 millimeter thick, - 0.4521 u 
Resistance of a i-inch cube, - - 13-98 microhms. 
Approximate percentage resistance per degree 

C. (i.S°F.at2o° C. 68° F.) - - 0.3S9 percent. 

Electro-chemical equivalent (hydrogcn=. 0105). 2560 
Sec Thcrmo-Eledric Series.) 

Anvil. An intermittent contact, or 4i make and break " of the 
current is sometimes produced by directly pressing a key down 
upon a metallic surface, the two being terminals of the circuit. 
The surface or stud on which such pressure is produced is called the 
anvil. The ordinary telegraph key, which makes a contact by the 
pressure of the operator's fingers does it by making a contact be- 
tween a contact piece upon the front end of the key and the anvil. 
In the induction coil the anvil is also found. Thus in the cut 
representing the end of an induction coil and its circuit breaker 
in which O and O' and P and / J/ represent the secondary circuit ter- 
minal connections A is the core of soft iron wires, // is the anvil ; the 
hammer when resting upon it so as to be in contact closes the cir- 
cuit. When the current coming from the primary to the post /, 
- through the hammer and anvil //, and emerges by ;;/, it 
etizea the core ; this attracts the hammer, which is made 
is armed with a mass of iron. This breaks the circuit. The ham- 



38 STANDARD ELECTRICAL DICTIONARY. 

met falls at once on the anvil, again making the circuit, and the 




Fig". 17. Induction Coil Circuit Breaker. 

action is repeated with great rapidity. Hammer and anvil or key 
and anvil contacts should be made of platinum. 

A. 0. C. Abbreviation for Anodic Opening Contraction, q. v. 

Aperiodic, adj. In an oscillating apparatus, or in the oscillating 
member of apparatus, the fact of having no reference to time of 
vibration ; aead-beat. 

Synonym. Dead-beat. 

Arago's Disc. An apparatus consisting of a disc of copper 




Fig. 18. Arago's Disc. 



STANDARD ELECTRICAL DICTIONARY. 59 

mounted, horizontally, or on a vertical spindle, and so arranged as 
to be susceptible of rapid rotation. Immediately over it, and best 
with a pane of glass intervening, a magnetic needle is mounted on 
a pivot directly over the axis ol the disc. If the disc is rotated the 
lines of force of the magnet are cut by it, and consequently currents 
are produced in the copper. These currents act upon the needle 
ami cause it to rotate, although quite disconnected. It is advisable 
for the needle to be strong and close to the disc, which should 
rotate rapidly. 

Arc. :'. To form a voltaic arc. 

Arc, Compound. A voltaic arc springing across between more 
than two electrodes. 

Arc, Metallic. The voltaic arc produced between terminals or 
electrodes of metal. The characteristics of such arc as contrasted 
with the more usual arc between carbon electrodes are its greater 
length for the same expenditure of energy, its naming character 
and characteristic colors due to the metals employed. It is some- 
times, for the latter reason, used in spectroscopic investigations. 

Arc Micrometer. A micrometer for measuring the distance 
between the electrodes of a voltaic arc. 

Arc, Simple. A voltaic arc produced, as usual, between only 
two electrodes. 

Arc, Voltaic. The voltaic arc is the arc between two carbon 
electrodes slightly separated, which is produced by a current of 
sufficient strength and involving sufficient potential difference. 
The pencils of carbon are made terminals in a circuit. They are 
first placed in contact and after the current is established they are 
separated a little. The current now seems to jump across the inter- 
val in what sometimes appears an arch of light. At the same time 
the carbon ends become incandescent. As regards the distance of 
separation with a strong current and high electro-motive force, the 
arc may be several inches long. 

The voltaic arc is the source of the most intense heat and bright- 
est light producible by man. The light is due principally to the 
incandescence of the ends of the carbon pencils. These arc differ- 
ently affected. The positive carbon wears away and becomes 
roughly cupped or hollowed ; the negative also wears away, but in 
some cases seems to have additions made to it by carbon from the 
>. All ill is is best seen when the rods are slender 
compared to the Length of the arc. 

It u undoubtedly the transferred carbon dust which has much to do 
with its formation. The conductivity of the intervening air is due 



4o 



STANDARD ELECTRICAL DICTIONARY. 



partly, perhaps, to this, but undoubtedly in great measure to the in- 
tense heating to which it is subject. But the co-efficient of resistance 
of the intervening air is so much higher than that of any other part 




Fig. 



Experimental Apparatus for Producing the Voltaic Arc. 



of the circuit that an intense localization of resistance occurs with 
corresponding localization of heating effect. This is the cause of 
the intense light. Thus if the carbons arc but 1-32 of an inch apart 
as in a commercial lam]) the resistance may be 1 14 ohms. The 
poor thermal conductivity of the carbon favors the concentration of 
heat also. The apparent res : stancc is too great to be accounted for 
by the ohmic resistance of the interposed air. A kind of thermo- 
electric effect is produced. The positive carbon has a temperature 
of about 4,000° C. (7,232° F. N t, the negative from 3,000° C. (5,432° F. ) 
to 3,500° C. (6,322° F.). This difference of temperature produces a 
counter-electro-motive force which acts to virtually increase the 
resistance of the arc. The carbon ends of an arc can be projected 
with the lantern. Globules are seen upon them due to melted 
silica from the arc of the carbon. 



STANDARD ELECTRICAL DICTIONARY. 



41 



Fip. 20. 
Areometer 



Areometer. An instrument for determining the specific 
gravity ot a fluid, It consists of an elongated body ballast- 
ed so as to Boat vertically and provided with a mark or a 
scale. It floats deeper in a light than in a heavy liquid. If 
it carries but one mark weights are added until that mark 
is reached, when the weights required give the specific 
gravity. Or the scale may give the reading directly based 
upon the depth to which it sinks. Areometers are often 
made of glass, ballasted with shot or mercury enclosed in 
their bottom bulb as shown. They are used in regulating 
battery solutions, and in watching the charging and dis- 
charging of storage batteries. [Synonym — Hydrometer.) 

Areometer, Bead. A tube of glass containing beads of 
different specific gravities. It has apertures at top and bot- 
tom. When immersed in a liquid, the same fills it, and 
the specific gravity within certain limits, depending on the 
factors of the beads, is shown by the beads which float and 
those which sink. It is used for storage batteries and other 
purposes where acids and solutions have to be 
tested. 

Argyrometry. The method of ascertaining 
the weight and inferentially the thickness of an 
electroplater's deposit of silver. It is done by 
weighing the article before and after plating. 

Arm. The four members of a Wheatstone 
bridge, q. v., are termed its arms. Referring 
to the diagram of a bridge, P t 0> R, S } are the 



Armature, [a.) A mass or 
piece of iron or steel, or a 
collection of pieces of iron 
designed to be acted on by a 
magnet. While nickel or 
cobalt might be used, they 
rarely or never are except 
in experimental apparatus. 
The armature of a permanent 
horse shoe magnet is simply 
a little bar of soft iron. When 
the magnet is not in use it is 
kept in contact with the poles 
with the idea of retaining 

its magnetism. It is then 
I to be used a- a keeper. 

Fig>22 . r , A bar magnet docs not 

' rally have an armature. 




42 STANDARD ELECTRICAL DICTIONARY. 

The armature is also used to exhibit the attraction of the magnet. 
Sometimes an armature is made of steel and is permanently mag- 
netized. Such an armature, termed a polarized armature, is repelled 
when its like poles are opposed to like poles of the magnet and 
otherwise is attracted with force due to the sums of the magnetism. 
If the magnet is sufficiently powerful depolarization of the arma- 
ture may ensue when like poles are opposed to like poles. Polarized 
armatures are used in various appliances, magneto generators, 
telegraphic instruments and others. 

(b) In a dynamo or Motor the mass of laminated iron or of wire 
which carries the coils of insulated wires which are caused to 
rotate in the field of force of the field magnets in order to establish 
and maintain potential difference with its accompanying current, or 
which rotates under the effects of a current in a motor. 
Dynamo Electric Generator.) 

The work of the armature core is twofold. It acts as a portion of 
the magnetic circuit, conducting the lines of force, and by virtue 
of its high permeability or multiplying power concentrating a 
number of the lines of force through its own substance. To enable 
it to act with efficiency in this direction it should be made of iron 
of the highest permeability, and should approach as closely as 
possible to the armature cores consistent with leaving space for the 
wire winding. It next acts as a support for the wires which arc- to 
be swept through the field of force. Thus it acts both to establish 
a strong field and then acts as a carrier for the wires which arc t<> 
be cut by the wires in question. In connection with this subject 
the different definitions under Armature, Dynamo % Commutator, 
Induction and similar topics may be consulted. 

(c) See Armature of Influence Machine* 

(d) See Armature of Leyden Jar or Static Condenser. 

Armature, Bar. An armature in a dynamo or motor whose 
winding is made up of conductors in the form of liars, 
round, rectangular and of other sections. This type of armature con- 
ductor is objectionable as Foucault currents are produced in it. It 
is found best to laminate or subdivide low resistance armature wind- 
ings. 

Armature, Bipolar. An armature in which two poles are in- 
duced by the field. A bipolar field magnet produces a bipolar 
armature. 

Armature Bore. The cylindrical space defined by the pole 
pieces of a dynamo or motor within which the armature' rotates. 

Synonym — Armature Chamber. 



STANDARD ELECTRICAL DICTIONARY. 43 

Armature, Closed Coil. An armature for a motor or dvnamo, 




Fig. 2^. Closed Coil Gramme Ring Armature. 

the ends of all of whose coils are united, so as to be in one closed 
circuit all the way around. 

Armature Coil, or Coils. The insulated wire wound around 
the core of the armature of an electric current generator or motor. 

Armature Core. The central mass of iron on which the insu- 
lated wire, to be rotated in the field of an electric current generator 
or motor, is wound. (See Dyyiamo-electric Machine and Motor, 
Electric. ) 

Armature, Cylinder. An armature of the Gramme ring type, 
but longer in the axial direction, so that its core resembles a long 
hollow cylinder, the wire being wound inside and outside as in the 
Gramme" ring. (See Gramme Ring.) 

Armature, Disc, (a) An armature of a dynamo electric machine 
or motor in which the coils arc wound so as to be flat and are car- 
ried mi the face of a disc forming the core or part of the core of 
the armature. S. P. Thompson treats it as a modified drmn 
armature extended radially, the outer periphery corresponding to 
the back end of the drum. The poles of the field arc generally 
placed to face the side or sides of the disc. 

(6) Another type of disc armature lias its wire wound on bobbins 
g ed around the periphery ofa disc. 

In di^e armatures there is often no iron core, their thinness ena- 
bling this to be dispensed with. 



44 STANDARD ELECTRICAL DICTIONARY, 




¥ig. 24. Disc Armature of Fritsche Machine, 
1 




Fig. 25. Plan of Winding Pacinotti's Disc Armature. 
Armature, Discoidal Ring. In a dynamo an armature of the 



STANDARD ELECTRICAL DICTIONARY. 



45 



shape of a ring of considerable radial depth of section as compared 
to its axial depth. It is generally made of iron ribbon or thin 
band wound to the proper size. 

Synonym — Flat Ring Armature. 

Armature, Drum. An armature for a dynamo or motor, con- 
sisting of a cylinder of iron preferably made up of discs insulated 
from each other by thin shellacked paper, or simply by their oxid- 
ized surfaces, and wound with wire parallel to the axis where it 
lies on the cylindrical periphery and crossing the heads approxi- 
mately parallel to the diameter. It operates practically on the 
same principle as a Gramme Ring Armature. (See Gramme Ring .) 

Synonym — Cylindrical Armature. 

Armature Factor. The number of conductors on an armature, 
counted or enumerated all around its external periphery. 

Armature, Hinged. An armature piyoted to the end of one 

of the legs of an electro-magnet so as to be free to swing and 
bring its other end down upon the other pole. 





Fig. 26. Hinged Armatures of Club-foot Electro Magnets. 

Armature, Hole. An armature whose core is perforated to 
secure cooling. 

nyni— perforated Armature. 

_ Armature, Intensity. An armature wound for high electro-mo- 
tiye force. A term little used at the present time. 

Armature Interference. A limit to the ampere turns per- 
missible on a given armature is found in the increase of cross mag- 



46 



STANDARD ELECTRICAL DICTIONARY. 



netizing effect, q. v., the increased lead necessitated, and the 
growth of the demagnetizing power. All such perturbing effects 
are sometimes expressed as armature interference. 

Armature, Load of. The circumflux, q. v., of the armature, or 
the ampere turns of the same. The maximum load which can be 
carried by an armature without sparking is directly proportional to 
the radial depth of core and to the length of the gap, and in- 
versely proportional to the breadth of the polar span. 

Armature, Multipolar. An armature in which a number of 
poles greater than two is determined by the field. A multipolar 
field is employed for its production. 

Armature, Neutral. An armature of a magnet or telegraph 
relay which is not polarized or magnetized. 

Synonym — Non-polarized Armature — Neutral Relay Armature. 

Armature of Influence Machine. Pieces of paper pasted on 
the stationary plate of an electric machine of the Holtz type 

Armature of Leyden Jar or Static Condenser. The inner 

and outer tin-foil coatings of a Leyden jar or other condenser. 

Armature, Open Coil. An armature of a dynamo or motor on 
which the coils are not joined in one closed circuit, but have their 




Fig. 27. Open Coil Ring Armature. 

ends or some of them separated, and connected each to its own com- 
mutator bar or each set to their own bar. 



STANDARD ELECTRICAL DICTIONARY. 47 

Armature, Pivoted. An armature for an electromagnet 
mounted on a pivot, which is at right angles to the yoke or parallel 
with the legs of the magnet, so as to be free to rotate. When 
the magnet is excited the armature is drawn into line or approxi- 
mately so with Us base or yoke. The system is used in some tele- 
graph apparatus. 

Armature Pockets. Spaces or recesses in armatures provided 
for the reception of the coils. 

Armature, Polarized. An armature made of steel or having a 
steel core to which permanent magnetism has been imparted. Such 
are used in some forms of magneto current generators, and in tele- 
graphic instruments. (See Ktlay^ Polarized.} 

Armature, Pole. An armature having coils wound on separate 
poles projecting radially all around the periphery of its central 
hub or disc, or projecting internally from a ring-like frame, their 
ends facing the field magnet. 

Synonym — Radial Armature. 

Armature, Quantity. An armature of a dynamo or motor 
wound for current of large quantity. The term is now but little 
used. 

Armature=Reactions. When an armature is running in an 
active dynamo a series of reactions is established, the more impor- 
tant of which are : I. A tendency to cross-magnetize the armature. 
II. A tendency to spark at the brushes. III. A tendency for the 
armature current to demagnetize on account of the lead which has 
to be given to the brushes. IV. Variations in the neutral points 
as more or less current is taken from the machine. V. Heating of 
armature, both core and conductors, and of pole pieces, which 
heating is due to Foucault currents. 

Armature, Revolving, Page's. An early form of motor. The 
field is produced by a permanent magnet. Above its poles is a 
soft iron armature wound witli a coil of insulated wire. A two- 
part commutator with contact springs conveys the current to the 
coil. The whole is so arranged that the polarity of the armature, 
as Induced by the coil, through which a current is passed, is reversed 
;. ) by the poles of the magnet. Then it is repelled 
from t: ad swings through [8o° to have its polarity reversed 

and to go through the- next l8o°, and so on. Thus it rotates at a 
very high rate of speed. 

•wing the elevation . /, B t is the armature- ; 
- or brushes ; //, the commutator with its sections 0, /. \\\ 



48 



STANDARD ELECTRICAL DICTIONARY. 



the section of the commutator W, IV, designate the springs or 
brushes, A, the vertical spindle carrying the armature and commu- 
tator, and S, S, the commutator sections. 




Fig. 28. Page's Revolving Armature. 



Fig. 29. 

Section of Commutator of Page's Revolving Armature. 

W, fV, Brushes ; A , Spindle ; S, S, Armature Segments. 



Armature, Ring. An armature whose core is in the shape of a 
ring, as the Gramme Ring Armature. (See Figs, jj & j;.) 



STANDARD ELECTRICAL DICTIONARY. 



49 




Fig-. 30. Rolling or 
Wbkrl Armature. 



Armature, Rolling, (a) An armature for 

a permanent horseshoe magnet consisting of a 
straight cylinder of soft iron on which a 
heavy wheel is mounted. When the legs of 
the magnet are inclined downward and the 
bar is laid across them it rolls down to the 
poles, across their ends, and hack up the 
under side. It is merely a magnetic toy or 
illustrative experiment. 

Synonym —Wheel Armature. 

[6) Another form consists of 
little bars of iron with brass 
discs attached to the ends. On 
placing two of these together 
and bringing the poles of a 
magnet near them, as shown, 
they become magnetized with 
like polarity by induction and 
repel each other, rolling away 
in opposite directions. 

Fig. 31. Rolling Ar- 
matures. 




Armature, Shuttle. The original Siemens' armature, now dis- 
carded. The core was long and narrow, and its cross section was 
nearly of the section of an H. The grooves were wound full of 
wire, so that the whole formed almost a perfect cylinder, long and 
narrow comparatively. (See Winding Shuttle.) 

Synonym — Siemens' Old Armature — Girder Armature — H Arma- 
ture. 




Fig". .'. Shuttle or H Arm.-. 

Armature, Spherical. An armature of a dynamo which is 
wound on a spherical coi to be almost a sphere. It is 

employed in the Thomson-Houston dynamo, being enclosed in a 
cavity nearly fitting it, formed by the pole pieces. 

Armature, Stranded Conductor. A substitute for bar anna 

turos in which stranded copper wire conductors arc substituted for 
lid bar conductors, to avoid Foucault currents. .See . \) tua- 



50 STANDARD ELECTRICAL DICTIONARY. 

Armature, Unipolar. An armature of a unipolar dynamo. 
(See Dynamo Unipolar.) 

Armor of Cable. The metal covering, often of heavy wire, sur- 
rounding a telegraph or electric cable subjected to severe usage, as 
in submarine cables. 

Synonym — Armature of Cable. 

Arm, Rocker. An arm extending from a rocker of a dynamo or 
motor, to which arm one of the brushes is attached. (Sec Rock- 
er.} Ordinarily there are two arms, one for each brush. 

Articulate Speech. Speech involving the sounds of words. It 
is a definition which has acquired importance in the Bell telephone 

litigations, one contention, concerning the Bell telephone patent, 

holding that the patentee did not intend his telephone to transmit 
articulations, but only sound and music. 

Astatic, adj. Having no magnetic directive tendency due to 
the earth's magnetism. Examples arc given under Astatic 
Needle; Circuit, Astatic; and Galvanometer Astatic. 

Astatic Needle. A combination of two magnetic needles so 
adjusted as to have as slight directive tendency as possible. Such a 
pair of needles when poised or suspended will hardly tend to turn 
more to one point of the compass than another. The combina- 
tion is generally made up of two needles arranged one above the 

other, with their poles in opposite 
directions. This combination is 
usually called Nobili's pair. If of 
equal strength and with parallel 

magnetic axes of equal length they 
would be astatic, in practice this 
is very rarely the case. A result- 
ant axis is generally to be found 
which may even be at right angles 
S {Jl N *° *- nc l° n 8 ax ^ s °f the magnets, 

causing them to point east and 
Fig. 33. Nobili's Pair. west. Such a compound needle 

requires very little force to turn it 
one way or the other. If one of the needles is placed within a coil 
of insulated wire a feeble current will act almost as strongly to 
deflect the system as if the other was absent, and the deflection 
will only be resisted by the slight directive tendency of the 
pair of needles. This is the basis of construction of the 
astatic galvanometer. Sometimes coils wound in opposite 
directions and connected in scries, or one following the other, sur- 




STANDARD ELECTRICAL DICTIONARY. 



5i 




Fig. 34. 

Vertical Pair Astatic Com- 

11 nation. 



round both needles, thus producing a still greater effect of deflection. 

Other astatic needles are shown in the cuts below. 

Asymptote. A line continuously approached by a curve, but 

which the curve, owing to its construction or nature of curvature, 
can never touch, be tangent to, or intersect. 

Atmosphere, (a) A term applied to 
the atmospheric pressure as a practical 
unit of pressure equal to 15 lbs. to the 
square inch as generally taken. It is 
really about 14.7 lbs. per square inch, 
or 1,033 grams per square centimeter. 

[fr) Air, q. v. 

Atmosphere Residual. The atmos- 
phere left in a vessel after exhaustion. 
The term may be applied to any gas. In 
an incandescent lamp after flashing 
the residual atmosphere consists of hydro-carbons. 

Atmospheric Electricity. The electricity of the atmosphere, 
rarely absent, but often changing in amount and sign. Benjamin 
Franklin, in a memoir published in 1749, indicated 
the method of drawing electricity from the clouds 
by pointed conductors. In June, 1752, he flew a 
kite and by its moistened cord drew an electric spark 
from the clouds, confirming his hy pothesis that light- 
ning was identical with the disruptive discharge of 
electricity. To observe electricity in fine weather 
a gold-leaf or other electroscope may be connected 
to the end of a long pointed insulated conductor. 
The electricity during thunderstorms can be 
shown by a similar arrangement, or burning 
alcohol or tinder gives an ascending current of 
warm air that acts as a conductor. Quite elaborate apparatus for 
observing and recording it have been devised. Atmospheric elec- 
tricity is usually positive, but occasionally negative. When the 
Sky is cloudless it is always positive, increasing with the elevation 
and isolation of the place-. In houses, streets, and under trees no 
positive electricity can be found. In the Isle of Arran, Scotland, a 
- per foot of increase in elevation was found by 
Sir William Thomson. At sunrise the electrification of the air is 
wards noon and deer* ases again to reach a sec- 
ond maximum a few hours after sinwt. It increases with the baro- 
metric generally. In cloudy weather it is sometimes nega- 
tive and the sign often chi :al times in the same day. In 

a thunderstorm the changes in sign and potential arc very rapid. 
Thee tricity is far from clear, 'fait attrib- 



N 



Fig. 35. 

Simple Astatic 

Needle. 



52 STANDARD ELECTRICAL DICTIONARY. 

utes it to a contact effect between air and water vapor, Solmcke 
to friction of water vesicles against ice particles in the upper 
atmosphere, he first showing that the two may coexist. The cause 
of the enormous increase of potential producing lightning is attrib- 
uted to the decreased capacity due to the change of water from 
cloud vesicles to drops, thus diminishing the electrostatic capacity 
of the water in question. (See Lightning* \ 

Atom. The ultimate particle or division of an elementarv sub- 
stance ; the smallest part that can exist in combination, and one 

which cannot exist alone. An elementarv substance is composed 
of molcculesjust as truly as a compound one, but the atoms in the 
molecule of an elementary substance arc all precisely alike. Hence 
atoms are the units of chemistry, they have to do with combinations, 
but the physical unit, the smallest particle of matter that can have 
an independent existence, is the molecule. The two are often con- 
founded, especially bv writers of a few years ago, so that by " atom 
the molecule is often meant. There is nothing to be said of their 
size or mass. All such calculations refer to the molecule, q, v.. 
often spoken of and called the atom. 

Atomic Attraction. The attraction of atoms for each other, in 
virtue of which they combine- into molecules ; chemical affinity, 
q. v., treats principally Of this, although molecular attraction also 

plays a part in it. 

Atomic Heat. The product of the atomic weight Of a substance 
by its specific heat. This product is approximately th . 4 ; 

this approximation is so dose that it is of use in determining the 

valency and atomic weights of substances. The atomic weight of 

a substance therefore represents the approximate number ofgram- 
calories required to raise one gram-atom, q« v., of such substance 
through i°C. (1.8° F.) 

Atomicity. The quantivalcncc or valency of the atoms ; the 
number of combination bonds, or bonds of affinity, possessed by the 
atoms of any substance. Thus two atoms of hydrogen combine 
with one atom of oxygen, and three of oxygen with one of sulphur, 
forming saturated compounds. Therefore, taking hydrogen Bfl 
single atomicity or a monad, oxygen is of double atomicity or a dyad, 
and sulphur is of six-fold atomicity, or a hexad. The elements are 
thus classified into seven seven orders of atomicities, thus : 

1, Monads or Univalent elements, Hydrogen, etc. 

2, Dyads or Bivalent " Oxygen, etc. 

3, Triads or Trivalcnt " Nitrogen, etc. 

4, Tetrads or Quadrivalent " Lead, etc. 

5, Pentads or Quinquivalent " Phosphorous, etc. 

6, Hexads or Sexivaleut " Sulphur, etc. 

7, Heptads or Septivalent " Chromium, etc. 



STANDARD ELECTRICAL DICTIONARY., 53 

The same element often possesses several atomicities. Barium 
is generally a dyad, sometimes a tetrad ; nitrogen acts as a monad, 
dyad, triad, tetrad and pentad. The familiar electrolysis of water, 
giving two volumes of hydrogen to one of oxygen, is one of the 
illustrations of the theory indicating that two atoms of hydrogen arc 
combined with one of oxygen. 

Atomic Weight. The number expressing the relative weight 
of the atom of any substance, that of hydrogen being generally 
taken as unity. This is the universal system, although any other 
element might be taken as the basis of the system. The whole 
theory of atomic weights is based on the indivisibility of the atom 
and on the theory of atomicity, q. v. ^See Equivalents.) 

Attraction. The tendency to approach and adhere or cohere, 
shown by all forms of matter. It includes gravitation, cohesion, 
adhesion, chemical affinity and other forms, and is opposed by 
repulsion, and is sometimes overcome by it, although it may be 
assumed to be always present. See the different kinds of attractions 
under their titles : Atomic Attraction ; Electro-magnetic Attrac- 
tion and Repulsion ; Electro Static Attraction and Repulsion ; 
Eleclro-druamic Attraction and Repulsion ; Magnetic Attraction 
and Repulsion ; Molar Attraction. 

Audiometer. An apparatus for obtaining a balance of induction 
from two coils acting upon a third. The third is placed between 
the other two and is free to move towards either. A scale is pro- 
vided to show the extent of its movement. A varying or interrupted 
current being passed through the two outer coils, the prepon- 
derating current will produce the most induction if the central coil 
is equidistant. It can always be moved to such a point that there 
will be no inductive effect, one counteracting the other. Thus its 
position measures the relative induction. A telephone is in cir- 
cuit with the intermediate coil and is used to determine when its 
position is such that no current is induced in it. It is sometimes 
used as a direct test of hearing. (See Hughes' Induction Balance. I 
nonym — Acoutometer. 

Aura, Electrical. The blast of air produced at highly electrified 
poir. 

Aurora. A luminous display seen in the nothern heavens in 
the- northern hemisphere, when it is the Aurora Horea/is, and seen 
in the southern heavens in the southern hemisphere, where it is called 
1 1 Australis % or indifferently for either, the Aurora Polaris* 
It takes the form of pale luminous bands, rays and curtains varying 
Near the poles they are very numerous. A French COm- 
1 150 auroras in 200 days. Their height is van- 
ned at from 90 to 460 miles ; they arc most frequent 



54 STANDARD ELECTRICAL DICTIONARY. 

at the equinoxes and least so at the solstices. There is a secular 
variation also, they attain a maximum of occurrence every n years 
together with sun spots, with a minimum 5 or 6 years after the 
maximum. There is also a period of 60 years, coincident with 
disturbances in the earth's magnetism. Various attempts have 
been made to account for them. They have a constant direction 
of arc with reference to the magnetic meridian (q. v. | and act upon 
the magnetic needle ; in high latitudes they affect telegraph circuits 
violently. There is a strong probability that they represent elec- 
tric currents or discharges. De la Rive considers them due to elec- 
tric discharges between the earth and atmosphere, which electricities 
are separated by the action of the sun in equatorial regions. Ac- 
cording to Balfour Stewart, auroras and earth currents (q. v. i may 
be regarded as secondary currents due to small but rapid changes in 
the earth's magnetism. The subject is very obscure. Stewart 
treats the earth as representing the magnetic core of an induction 
coil, the lower air is the dielectric, and the upper rarefied and 

therefore conducting atmosphere is the secondary coil. This makes 
the aurora a phenomenon of induced currents. Then the sun may 
be regarded as the instigator of the primary changes i.i the earth's 
lines of force representing the primary of an induction coil. 

Austral Pole. The north pole of the magnet 19 thus called 
sometimes in France ; the austral pole of a magnet is the one which 
points towards the north polar regions As unlike magnetic p 

attract each other, it is but rational tOCall the north-seeking poleof 
the magnet the south or t lust) dl Pole* In the same nomenclature 
the SOUth pole of a magnet, or the south-seeking pole, is called 

the Boreal Pole. 
A. W. G. Abbreviation for American Wii [. v. 

Axis, Electric. The electric axis of a pyroeleetrie crystal; BUCh 
as a tourmaline crystal ; the line connecting the poi 

pvroelcctric excitability. 

Axis of Abscissas. In a system of rectilinear, or right angle 
co-ordinates, the horizontal axis. | See ( b-ordinates,) 
Synonym — Axis of X. 

Axis of Ordinates. In a system of rectilinear right angle co-or- 
dinates, the vertical axis. ^Sce Coordinates*) 

Synonym — Axis of Y. 

Azimuth. The angle between the plane of the meridian and the 
plane of an azimuth circle, q. v. 

Azimuth Circle. A great circle, whose plane passes through the 
zenith or point of the heavens directly overhead ; any great circle in 
whose plane the vertical at the point of observation is included. 

Each celestial body has or determines an azimuth circle. 



STANDARD ELECTRICAL DICTIONARY. 55 

B. a) Abbreviation for Bcaume\ a hydrometer scale. (See 
:c.) Thus io c B. means H ten degrees Bcaumc." 

[o) Symbol for the coefficient of induced magnetization, or the 
number of lines per square centimeter induced in a magnetic cir- 
cuit or in any specified part of it. 

B. A. Abbreviation for British Association. It is prefixed to 
standards fixed by the committee of the British Association for the 
Advancement of Science. Thus the B. A. ohm means the British 
Association ohm, a measure of resistance which is equal to the 
resistance of a column of mercury 104.9 centimeters long and one 
square millimeter area of cross-section. (Sec Ohm.) 

Back Induction. A demagnetizing force produced in a dyna- 
mo armature when a lead is given the brushes. The windings by 
such setting of the brushes are virtually divided into two sets, one a 
direct magnetizing set, the other a cross magnetizing set. The latter 
have a component due to the obliqueness of the neutral line, which 
component is demagnetizing in its action. 

Back Shock or Stroke of Lightning. A lightning stroke 
received after the main discharge of the lightning, and caused by 
a charge induced in neighboring surfaces by the main discharge. 
The discharge aifects the evenness of distribution of surrounding 
surfaces so that a species of secondary discharge is required to 
make even the distribution, or to supply charge where needed to 
bind an opposite one. The effects are much less severe as a rule 
than those of the main charge, although the back stroke has caused 
death. The back stroke is sometimes felt a considerable distance 
from the place of the original lightning stroke. 

Synonym — Return Stroke. 

BackStroke. [a] In telegraphy the return stroke of the lever 
in a telegraph sounder, striking the end of the regulating screw with 
a sound distinct from that which it produces on the forward stroke 
as it approaches the magnet poles. It is an important factor in 
receiving by ear or sound reading. 

(b) See Bach Shock or Stroke of Lightning. 

Balance, (a) Wheatstone's Bridge, q. v., is sometimes termed the 

trie Balance. 

(b) A suspension or torsion balance is one which includes a fila- 
ment or pair of filaments to whose lower end or ends arc attached 
a horizontal indicator often called a needle, or a magnetic needle. 

Balance.} 

(c) See Induction Balance, Hugh 

(d) For Thermic Balance, sec Bolonu 

(e) Sec Balance, si nip- \ 



56 STANDARD ELECTRICAL DICTIONARY. 

Balance, Ampere. A class of electrical measuring instruments 
due to vSir William Thomson may be grouped under this head. 

The instrument is a true balance or scales such as used for weigh- 
ing. It is supported by a torsional wire support in place of knife 
edges. At each end it carries a circle of wire through which the 
current to be tested is passed. The torsional wire support enables 
the current to be carried to these wire rings. Above and below each 
of these rings are two similar rings, also connected so as to receive 
the current. They arc BO connected that the current shall 
through them in opposite senses. When a current passes, there- 
fore, one of these rings repels and one attracts the balanced ring. 

The extent of this action measures the intensity of the current. 
A sliding weight moving along a graduated scale on the balance 
is used to bring the balance beam into equilibrium when the current 
is passing. The degree of displacement of this weight gives the 
strength of the current in amperes. 

These balances are made for different currents. Thus there is a 
centi-ampere balance, deka-ampere balance andothei '.las 

an ampere balance. 

Batata. A gum used as an insulating material. It is the inspis- 
sated juice of a sapotaceous tree, tin- bullet tree, Mimusops gloih 
of tropical America, from the Antilles to ( Wiiana. It is intermediate 
in character between caoutchouc and guttapercha. It is superior 
to gutta pcrcha in some respects, being very slightly acted on bv 
Light. 

Synonym — Chicle. 

B. & S. W. G. Abbreviation for brown ,\: Sharpe Wire G 
the regular American Wire (range. See Wire Gauge % . Inion 

Barad. An absolute or fundamental unit of pressure, equal to 
one dyne per square centimeter. 

Barometer. An apparatus for measuring the pressure exerted 
by the atmosphere. It consists, in the mercurial form, of a glass 
tube, over 31 inches long, closed at one end, filled with mercury 
and inverted, with its Open end immersed in a cistern of mercury. 
The column falls to a height proportional to the pressure e>f the 
atmosphere from 30 to 3 1 inches at the sea level. The "standard 
barometer " is a height of the mercury or of the " barometric col- 
umn " of 30 inches e>r 7(10 centimeters, measured from the surface 
of the mercury in the cistern. 

The column of mercury is termed the barometric column. Above 
it in the tube is the Torricellian vacuum. 

Bars of Commutators. The metal segments of a commutator 
of a dynamo or motor. They are made of bars of copper, brass or 
bronze insulated from one another. (See Commutah 

Synonyms— Segments, Commutator Segments, Commutator Bars. 



STANDARD ELECTRICAL, DICTIONARY. 57 

Bath, [a) In electro-plating the solution used for depositing metal 

bained in a vat or tank ; as a silver, copper, or nickel bath 

used lor plating articles with silver, copper, or nickel respectively. 

(p) In electro-therapeutics a bath with suitable arrangements, 
electrodes and connections for treating patients with electricitv. It 
is termed an electric bath or electro-therapeutic bath. 

Bath, Bipolar Electric. In electro-therapeutics a bath in 
which the electrodes are both immersed in the water. The patient 
placed between them receives part of the discharge. The elec- 
trodes are large copper plates, termed shovel electrodes. 

Bath, Electric Shower. An electro-medical shower bath. The 
patient is placed on a metallic stool or support connected to one 
of the electric terminals. Water slightly akaline is showered 
upon him. The other electrode is in connection with the water. 
The rain of drops and streamlets is the conductor of the current or 
discharge. 

Bath, Multipolar Electric. An electro medical bath with a 
number of electrodes instead of two. 

Bath, Stripping. In electro-plating a solution used for dissolving 
and thus removing the plating from any object. The stripping bath 
is of the same general type as the plating bath for the same metal 
as the one to be dissolved. The object to be " stripped " is made 
the anode of a plating circuit, and as the current acts the old plat- 
ing is attacked and dissolves, leaving the body of the article bare. It 
is simply the operation of plating reversed. The same term is 
applied to baths acting by simple solution. Stripping baths are 
described under the different metals as Silver Bath, Stripping — 
Gold Bath, Stripping. 

Bath, Unipolar Electric. An electro-medical bath, in which 
only one electrode connects with the water of the bath. The sec- 
ond electrode is supported above the bath. The patient touches 
this while in the water whenever electric action is desired. 

Batten. A strip of wood grooved longitudinally for holding 





Fig. 36. Three Wire M J, Two Wire Moulding or 

en. Ba i : 

apartments for electric light or power. In use 



58 



STANDARD ELECTRICAL DICTIONARY. 



they are fastened to the wall, grooves inward, or else grooves out- 
ward, with the wires lying in the grooves and coveted with the 
covering strip. For two wire work each batten contains two grooves; 
for the three wire system it contains three grooves. 
Synonym — Moulding. 

Battery. A combination of parts or elements for the produc- 
tion of electrical action. The term is principally applied to 
voltaic batteries, but there are also magnetic batteries, batteries of 
Leyden jars, and other combinations, described in their places, 
which come under this category. 

Battery, Acetic Acid. A battery whose active solution or 
excitant is acetic acid or vinegar. This acid has been used by Pul- 
vermacher in his medical battery, as being a substance found in 
every household in the form of vinegar. It is now but little used. 

Battery, Alum. A battery using as excitant a solution of alum. 
This battery has had sonic application for electric clocks, but only 
to a limited extent. 




Fig. 38. Balloon ok Flask Battery. 

Battery, Aluminum. A battery in which aluminum is the 
negative plate and aluminum sulphate the excitant. It is mounted 
like the gravity battery. Its electro-motive force is 0.2 volt. 



STANDARD ELECTRICAL DICTIONARY. 59 

Battery, Bagration, A battery with zinc and carbon elec- 
trodes immersed in earth sprinkled with sal ammoniac (ammonium 

chloride). The copper is preferably first immersed in sal ammoniac 
solution and dried, until a green layer is formed on its surface. 

The battery is highly praised for its constancy by De la Rive, 
but may be regarded as obsolete. 

Battery, Balloon. A form of gravity battery into whose centre 

a globular ilask, />', is inverted, which is filled before inversion 
with copper sulphate, of which 2 lbs. are used, and water, so as to 
remain full. This acts as a reservoir of copper sulphate, which it 
constantly supplies. The glass jar is closed with a perforated 
wooden cover. 

Battery, Banked. a A battery arranged to feed a number of 
separate circuits. 

{{>) A battery connected in parallel or in multiple arc. 

Battery, Bichromate. A battery -with amalgamated zinc and 
carbon plates, with an exciting fluid composed of sulphuric acid, 
water, and potassium bichromate. For formula of such solutions 
see Eleetropoion Fluid — Kookogey*s Solution — Poggcndorffs 
Solution — Trpuve's Solution — Dclauricr s Solution , and others. 
(See Index.) 

Battery, Bunsen. A two fluid porous cell battery. The nega- 
tive plate is carbon, the positive plate, amalgamated zinc. The 



f^i 




! I 



depolarizer is nitric acid or eleetropoion fluid, <\. v., in which the 
1 is immersed. The last named depolarizer or some eqniva- 



6o 



STANDARD ELECTRICAL DICTIONARY. 



lent chromic acid depolarizing mixture is now universally used. 
The excitant is a dilute solution of sulphuric acid. Originally 
the carbon was made cylindrical in shape and surrounded the 
porous cup, in which the zinc was placed. This disposition is 
now generally reversed. The electro-motive force is 1.9 volts. 
The depolarizing solution is placed in the compartment with the 
carbon. The excitant surrounds the zinc. 

Battery, Cadmium. A battery in which cadmium is the nega- 
tive plate, sulphate of cadmium solution the excitant and depol- 
arizer, and zinc the positive plate. Electro-motive force, 0.3] volt or 

about one third of a Daniell cell. It is mounted like a gravity 
battery. 

Battery, Callan. A modification of Grove's battery. Platinized 
lead is used for the negative plate, and as a depolarizer a mixture 
of 4 parts concentrated sulphuric acid, 2 parts of nitric acid, and 2 

parts of a saturated solution of potassium nitrate. 1 See Hattcry, 

ii rove's.) 

Battery, Camacho's. A battery with carbon negative and 

amalgamated zinc positive electrodes. The carbon is contained in 
a porous cup, packed with loose carbon. Blectropoion or other 
fluid of that type serves as excitant anddep* »lai l/.er, and is delivered 
as shown from cell to cell by syphons. 




Fig. 40. Camacho's Battery. 

Battery, Carre's. A Daniell battery for whose porous cup a 
vessel or species of sack made of parchment paper is substituted. 
The battery has been used for electric light, and has been run for 



STANDARD ELECTRICAL DICTIONARY. 



61 



200 successive hours, by replacing every 24 hours part of the zinc 

sulphate solution by water. 

Battery, Cautery. A battery used for heating a platinum wire 
or other conductor used for cauterization in electro-therapeutics. 

The term is descriptive, not generic. 

Battery, Chloric Acid. A battery of the Bunscu type in which 
an acidulated solution of potassium chlorate is used as depolarizer. 

Battery, Chloride of Lime. A battery in which bleaching powder 
is the excitant. The zinc electrode is immersed in a strong solu- 
tion of salt, the carbon in a porous vessel is surrounded with frag- 
ments of carbon and is packed with chloride of lime (bleaching 
powder). There is no action on open circuit. It has to be her- 
metically sealed on account of the odor. Its electro-motive force 
is — initial, 1.65 volts; regular, 1.5 volts. 

Synonym — Niaudet's Battery. 

Battery, Chromic Acid. Froperly a battery in which chromic 
acid is used as a depolarizer. It includes the bichromate battery. 
See Battery ) Bichromate.) 

Battery, Closed Circuit. A battery adapted by its construction 
to maintain a current on a closed circuit for a long time without 
sensible polarization. The term is merely one of degree, for any 
battery becomes exhausted sooner or later. As examples the Grove, 
Bunsen or Daniell batteries may be cited. 

Battery, Column. The original Volta's pile. It consists of a 
scries of compound circular plates, the upper or lower half, A % 
copper ; the other, Z, of zinc. Between each pair of plates some 




Fig. 41. COLUMN Battery. 

• Loth, /', u y is laid, which is saturated with dilute acid. 
wn in the cut, the parts are laid up in two piles, connected at 



62 



STANDARD ELECTRICAL DICTIONARY. 



the top with a bar, c } c, and with vessels of acidulated water, b y b y as 
electrodes. The great point in setting it up is to be sure that no 
acid runs from one disc of flannel to the next over the outside of 
the plates, as this would create a short circuit. The plates are best 
compound, being made up of a zinc and a copper plate soldered 
together. They may, however, be separate, and merely laid one on 
the other. In such case great care must be taken to admit no acid 
between them. 

Volta's pile is no longer used, except occasionally. Trouvi-'s 
blotting paper battery (see Battery y TroUTJ&'s) is a relic of it, and 
the same is to be said for Xamboni's dry pile. 

It rapidly polarizes, the flannel retains but little acid, so that it is 
soon spent, and it is very troublesome to set up. Great care must 
be taken to have the cloth discs thoroughly saturated, and wrung 
out to avoid short circuiting by squeezing out of the acid. 

Battery, D'Arsonval's. A battery of the Buusen type, differ- 
ing therefrom in the solutions. As excitant in which the zinc 

electrode is immersed, the following solution is used : 
Water, 20 volumes ; Sulphuric Acid (purified by shaking with a 

little olive or similar oil 1, 1 volume; hydrochloric acid, 1 volume. 

As polarizer in which the carbon is immersed the follow 
used : 

Nitric acid, 1 volume; hydrochloric acid, 1 volume; water acid- 
ulated with 1-20U1 sulphuric acid, 2 volumes. 

Battery, de la Rue. A battery with zinc positive and silver neg- 
ative electrode ; the depolarizer is silver chloride ; the excit 




r 



A* a 



Fig. 42. De la Rue's Battery. 

common salt or ammonium chloride. The cut shows one 
forms of construction. 

The right hand portion of the cut, Fig. 42, shows the zinc per- 



STANDARD ELECTRICAL DICTIONARY. 63 

forated at Cfor the connection from the next silver plate. The next 
to it is the negative electrode of silver around which a mass ot 
silver chloride is cast in cylindrical form. A is a parchment paper 
Cylinder with two holes near its top, through which the silver wire 
of the negative electrode is threaded', as shown in J>. A solution of 
25 parts ammonium chloride in 1,000 parts of water is the approved 
excitant. Its electro-motive force is 1.03 volts. 
The jars are closed with paraffin. 

Battery, Dry. [a) A form of open circuit battery in which 
the solutions by a mass of zinc oxyehloride, gypsum, or by a gelat- 
inous mass, such as gelatinous silica, or glue jelly, are made 
practically solid. Numbers of such have been patented, and have 
met with considerable success. 

(b) Zamboni's dry pile, q. v., is sometimes termed a dry battery. 

Battery, Element of. A term applied sometimes to a single 
plate, sometimes to the pair of plates, positive and negative, of the 
single couple. 

Battery, Faradic. A term applied, not very correctly however, 
to apparatus for producing medical faradic currents. It may be an 
induction coil with battery, or a magneto-generator worked by 
hand. 

Battery, Ferric Chloride. A battery of the Bunsen type, in which 
a solution of perchloride of iron (ferric chloride) is used for the 
depolarizing agent. A little bromine is added with advantage. 
The depolarizing agent recuperates on standing, by oxidation from 
the oxygen of the air. 

Battery, Fuller's. A battery of the Bunsen type. The zinc 
plate is short and conical, and rests in the porous jar into which 
some mercury is poured. An insulated copper wire connects with 
the zinc. A plate of carbon is in the outer jar. The solutions are 
used as in the Bunsen battery. 

Synonym — Mercury Bichromate Battery. 

Battery, Gas. a A battery whose action depends on the oxida- 
tion of hydrogen as its generating factor. It was invented by 
Grove. Plates of platinum are immersed in cups of dilute acid, 
arranged as if they were plates of zinc and carbon, in an ordinary 
battery. Bach plate is surrounded by a glass tube sealed at the 
t<»p. The tubes arc filled with acid to the tops. Through the 
top the eohnecti orrent from another battery is 

then passed thr mposing the water and surrounding 

the 11; with an atmosphere of oxygen 

with hydrogen. Considerable quantities of these 
gases are also occluded by the plates. On now connecting the 



64 



STANDARD ELECTRICAL DICTIONARY. 



terminals of the battery, it gives a current in the reverse direc- 
tion of that of the charging current. 

This battery, which is experimental only, is interesting as being 
the first of the storage batteries. (See Grove's Gas Battery.) 

(5) Upward's Chlorine Battery and any battery of that ly]> 
Battery, Upward's,) is sometimes termed a gas battery. 

Battery Gauge. A pocket or portable galvanometer for use in 
testing batteries and connections. 

Battery, Gravity. A battery of the Daniell type, in which the 
porous cup is suppressed and the separation of the fluids is secured 
by their difference in specific gravity. A great many forms have 
been devised, varying only in details. The copper plate, which is 
sometimes disc shaped, but in any case of inconsiderable height, 
rests at the bottom of the jar. Near the top the zinc plate, also 
flat or of slight depth, is supported. As exciting liquid 8 strong 
solution of copper sulphate lies at the bottom of the jar. This is 
overlaid by a solution of zinc sulphate, or sodium sulphate, which 
must be of considerably less specific gravity than that ofthecop- 
per sulphate solution. In charging the jar one-tenth of a saturated 
solution of zinc sulphate mixed with water is sometimes used as 
the upper fluid. This may be first added so as to half fill the jar. 
The strong solution of copper sulphate may then be added with a 
syphon or syringe underneath the- other so as to raise it up. from 
time to time copper sulphate in crystals are dropped into the jar. 
They sink to the bottom and maintain the copper sulphate solution 
in a state of .saturation. 




Fig. 43. Gravity Battery of the Trouve-Callaud Type. 

If the battery is left on open circuit the liquids diffuse, anel 
metallic copper precipitates upon the zincs. This impairs its 
efficiency and creates local action. As long as the battery is kept at 



STANDARD ELECTRICAL DICTIONARY. 



work on closed circuit work but little deposition, comparatively 
speaking, occurs. 

From time to time, in any case, the zinc plates arc removed and 
scraped, so as to remove the copper 
which inevitably forms on their sur- 
face. Care must be taken that the 
zinc sulphate solution, which is 
constantly increasing in strength, 
docs not get so strong as to be- 
come ot as high specific gravity as 
the copper sulphate solution. From 
time to time some of the upper solu- 
tion is therefore removed with a 
syphon or syringe and replaced with 
water. An areometer is useful in 
running this battery. 

Battery, Grenet. A plunge bat- 
tery with zinc positive and carbon 
negative electrodes. Electropoion 
or other chromic acid or bichromate 
solution is used as depolarizer 
and excitant. The zinc plate alone 
is plunged into and withdrawn from 
-olution. 




Fig. 



Grenet's Batterv. 



Battery, Grove's. 




Fig. 4^. Grove's Battery. 
nitric acid radical by the hydrogen 
in the spent liqn 



A two fluid galvanic batterv. A porous cup has 
within it a riband of platinum, which 
is the negative plate ; amalga- 
mated zinc in the outer jar is the 
positive plate. Dilute sulphuric 
acid (10 per cent, solution) is 
placed in the outer jar, and strong 
nitric acid (40 B.) as a depolar- 
izer in the porous cups. Its 
E. M. F. is 1.96 volts. 

It is objectionable, as it gives off 
corrosive nitrous fumes. These 
are produced by the oxidation of 
the nascent hydrogen by the nitric 
acid, by the following reaction : 

3H + HNO 2 II. o NO. 

There are other reactions, one <>f 

which results in the formation of 

ammonia by the reduction of the 

Ammonium can be detected 



66 STANDARD ELECTRICAL DICTIONARY. 

Battery, Hydrochloric Acid. A battery in which hydrochloric 
acid is used as the excitant. Many attempts have been made to 
use this acid in batteries, but the volatile nature of the acid car. 
the production of so much odor with corrosive funics that it has 
never come into use. 

Battery, Lead Chloride. A battery <>f the load sulphate type 
in which lead chloride is the depolarizer. It has had no extended 
use. 

Battery, Lead Sulphate. A battery similar to Marie Davy's 
battery orthe gravity battery, but using Lead sulphate as depolarizer 

and excitant. Lead, copper or tin is the mate-rial of the negative 
plate. Becqucrcl used the lead sulphate as a solid cylindrical 1: 
surrounding a lead rod 1-5 to % inch in diameter. One part ofcom- 
mon salt may be mixed with 5 parts of the had sulphate. The elec- 
tro-motive force is about o. 5 volt The resistance is very high. 

Battery, Leclanche. An open circuit battery with porous cup. 
In the outer jar is a zinc rod ; a carbon plate is placed in the porous 
cup. The latter is packed with a mixture of clean powdered man- 
ganese binoxide as depolarizer, and graphite in equal volumes. A 
strong solution of ammonium chloride (sal ammoniac) is placed in 
the outer jar. It is only used on open circuit work. Its elect 
motive force is 1.4S volts, when not polarized. 

The reaction is supposed to be about the following : 
2NH 4 Cl + 2 Mn ()_, -fZh = Zn CI, + 2 N II • H, O -f- M, 

The battery rapidly weakens on open circuit, but quickly recu- 
perates. There is another form of this battery, termed the agglom- 
erate battery. (See Battery^ Leclanchi , \g glomerate. \ 

Battery, Leclanche Agglomerate. A form of the Leclanche 
in which the porous jar is suppressed. Cakes made of a mixture of 
carbon, 52 parts ; manganese binoxide, 40 parts ; gum lac, 5 parts ; 

potassium bisulphate, 3 parts, compressed at 300 atmospheres, at a 
temperature of ioo° C. (21 2° P.), are fastened by India rubber bands 
or otherwise against the carbon plate. These constitute the depolar- 
izer. Various shapes arc given the carbon and depolarizing 
agglomerates. 

Battery, Local. A battery supplying a local circuit isce Circuit ', 
Local). The current is governed by the relay situated on the main 
line and operated by its current. 

Battery, Main. The battery used in operating the main line. 
It is usually applied to telegraphy. Its function is then to supply 
current for working relays, which in turn actuate the local circuits. 

Main and local circuits and batteries are also used in the auto- 
matic block system of railroad signalling. 



STANDARD ELECTRICAL DICTIONARY. 



67 




Fig. 46. Lecla.nche Battery. 



Battery, Marie Davy's. A two fluid porous cup battery 
with carbon negative plate, zinc positive plate, and mercury sul- 
phate, a nearly insoluble salt, as depolarizer and excitant. Mer- 
curous or mercuric sulphates have been used in it. Its electro- 
motive force is 1.5 volts. The local action and waste, owing to the 
slight solubility of the mercury compounds, is very slight. If used 
on close circuit it becomes polarized. It is also subject under 
extreme circumstances to reversal of polarity, zinc becoming 
ted upon the carbon, and there forming a positive electrode. 

In using the cells in series the level of Liquid in all must be the 
same, otherwise the cell in which it is lowest will become polarized 
and exhausted. 

Modifications of this battery on the lines of the gravity battery 
have been constructed. 

: Mercury Battery. 

Battery, Maynooth's. A battery of the Bunsen type, with 

ve plate. The iron takes the passive form and is 

not attacked. 

Battery, Medical. A term applied very indiscriminately to 
medical current \ J Induction coils, or to any 

source of electricity, static or current, for medical application. 



68 STANDARD ELECTRICAL DICTIONARY. 

Battery, Meidinger's. A variety of Daniell cell of the gravity 

type. The plates are cylindrical. The zinc plate lies against the 
upper walls of the vessel. The copperplate of smaller diameter rests 
on the bottom. A large tube, with an aperture in its bottom, is sup- 
ported in the centre and is charged with copper sulphate crystals. 

The cup is filled with a dilute solution of Epsom salts i magnesium 
sulphate) or with dilute sulphuric acid. 

Battery Mud. A deposit of mud-like character which forms in 
gravity batteries and which consists of metallic copper precipitated 

by the zinc. Jt indicates wasteful action. 

Battery, Multiple=connected. A battery connected in parallel, 

all the positive plates being connected to one electrode, and all 
the negative to another. 

Battery, Nitric Acid. A battery in which nitric acid is used 
as the excitant. Owing to its COSt and volatility this acid has been 
but little used in batteries, other than as a depolarizer. In (.rove's 

battery (sec Battery, Grove's it has been thus u>ed. 

Battery of Dynamos. A number of dynamos may be arranged 

to Supply the same circuit. They are- then sometimes termed as 

above, a Dynamo Battery. They may be arranged in series or in 
parallel or otherwise combined. 

Battery of Leyden Jars. To produce the quantity cfle v 
single large Leyden jar with a number of small ones they are often 
connected in parallel and termed a battery. In sue'h case the inner 

coatings are all connected by regular bar conductors, and the outside 

coatings are alse> all in connection. They are conveniently placed 

in a box or dee-]) tray whose inner surface- is lined with tinfoil, with 
an outside connection lor grounding, etc. The iasiiiiti\ q. v., 
arrangement is ne>t se> generally termed a battery. 

Battery, Open Circuit. A battery adapted for use in Open cir- 
cuit we>rk. Its main requirement is that it shall not run down, or 
exhaust itself when left on open circuit. The Lcclauchej battery is 
very extensively used for this work. Its action is typical of that of 
most open circuitbattcries. It is without any action on open circuit. 
It is very quickly exhausted on ch>sed circuit, but recuperates or 
depolarizes quite soon when on open circuit. It is always in con- 
dition for a momentary connection, but useless for stcaely we>rk. 

Battery, Oxide of Copper. A battery with zinc positive and 
iron negative electrodes. The excitant is a 30 or 40 per cent, sedi- 
tion of sodium or potassium hydrate (caustic soda or caustic potash . 
The depolarizer is copper oxide. In action the copper is gradun Un- 
reduced to the metallic state. The iron element is often the con- 
taining vessel. The battery is practically inactive on open circuit. 



STANDARD ELECTRICAL DICTIONARY. 69 

Its electro-motive force varies from .75 to .90 volt. To prevent the 

formation of sodium or potassium carbonate the cell should be 
closed, or else the Liquid should be covered with mineral oil. 

mytns — Lalande & Chaperon Battery — Lalandc-Edison bat- 
tery. 

Battery, Peroxide of Lead, A battery in which peroxide of 
lead ^lead binoxide) is the depolarizer. It is a sort of predecessor 
of the present secondary battery. 

Battery, Platinized Carbon. A modification of vSmec's bat- 
tery, in which platinized carbon is used for the negative plates. 
Before polarization the K. M. F. is equal to that of Smee's bat- 
tery. Polarization reduces its electro-motive force one-half. 

Battery, Plunge. A battery whose plates are mounted so as to 
be immersed in the battery cups or cells, when the battery is to be 
used, and withdrawn and supported out of the cups when not in 
use. The object is to prevent wasting of the plates by standing in 
the solution. It is a construction generally used with sulphuric 
acid — chromic acid solution and amalgamated zinc and carbon 
plates. 

Battery, Pneumatic. A battery arranged to have air blown 
through the solution to assist diffusion and depolarization. It is 
a construction applied to chromic acid or bichromate batteries. 

Battery, Primary. A battery in which the current is supplied 
by the solution of one of the plates by the solution. The term 
distinguishes it from a secondary or storage battery. 

Battery, Pulvermacher's Electro=Medical. In this battery 
the electrodes were zinc and copper wires wound upon small pieces 
of wood. Dilute vinegar was used as the excitant, because it could 
be found in every household. Formerly the battery had great suc- 
cess. It is now little used. 

Battery, Sal Ammoniac. Batteries in which a solution of 
ammonium chloride is the excitant ; they are very extensively 
used on open circuit work. (Sec lUittcry, Lcclanchc. < 

The crystals formed in these batteries have been analyzed and 
found to consist of ammonium zinc chloride, 3X110., 8 X II.., 4 H 2 C 

Battery, Salt, or Sea Salt. Batteries in which a solution of 

sodium chloride or common salt is the excitant, have been largely 

^•specially for telegraphic purposes. The Swiss telegraphs 

mbination with salt and water as the excitant. 

The batteries arc sometimes mounted as plunge Xhey 

arc exl f short circuiting after some hours, but recuperate 

ig. The zinc is not amalgamated. 



7o 



STANDARD ELECTRICAL DICTIONARY. 



Battery, Sand. A battery whose cells are charged with sand 
saturated with dilute acid. It prevents spilling of acid. It is now 
practically obsolete. 

Battery, Secondary. A voltaic battery whose positive and 
negative electrodes are formed or deposited by a current from a 
separate source of electricity by electrolysis. On disconnection the 
battery is ready to yield a current, in the reverse direction of that of 




Fip. 47. Secondary Hattf.kv. 

the charging current. The usual type lias lead plates on one of which 
lead binoxidc and 011 the other of which Bpongy lead is formed. 
The lead binoxide seems to be the negative element, and it also 
acts as the depolarizer. The spongy lead is the positive electrode. 
The solution is dilute sulphuric acid of specific gravity t . 1 7. The 
action consists first in the oxidation of the spongy lead. The hydro- 
gen set free by the reaction, and which by electrolytic transfer 
goes to the other plate, reduces the lead binoxide to protoxide. 
The sulphuric acid then attacks the oxides and converts the oxides 
into sulphates. 

The charging process consists in sending a current in the reverse 
direction through the battery. If there are several cells they are 
arranged in series, so that each one receives the same intensity of 
current. An electrolytic decomposition takes place, the lead sul- 
phate on one plate is reduced to metallic lead, and that on the 
other plate is oxidized to lead binoxide. It is then ready for use. 



STANDARD ELECTRICAL DICTIONARY. 



7i 



The plates in a lead plate battery are of very large area per cell, 
and are placed close together. Sometimes, as in Planters battery, 

large flat plates are laid together with a separating insulator between 
them, and are then rolled into a spiral. Sometimes, the most usual 
arrangement, the plates are in sets, the positive and negative ones 
alternating, and each cell containing a number of plates. 

To secure a good quantity of active material, the plates are some- 
times perforated, and the perforations arc filled with oxide of lead. 
This gives a good depth of material for the charging enrrent to 
act on, and avoids the necessity for a tedious tl forming," q. v. 

The electro-motive force of such a battery per cell is 2 volts. Its 
resistance may only be one or two-hundredths of an ohm. An 
intense current of many amperes can be supplied by it, but to avoid 
injuring the cell a current far less than the maximum is taken 
from it. 

To charge it, a slightly greater electro-motive force, the excess 
being termed spurious voltage, is required. 




Fig. 48. Siemens' and Halske's Paier Pulp Batthkv. 



7 2 



STANDARD ELECTRICAL DICTIONARY. 



Battery, Secondary, Planted. Plant's secondary battery is 
one of the earlier forms of storage battery, but has had much suc- 
cess. Two lead plates, large in area and close together but not 
touching, are "formed/* by exposure to an electrolyzing current of 
electricity in one direction, while they are immersed in dilute sul- 
phuric acid. This converts the surface of one plate into binoxide. 
The cell is then allowed to discharge itself almost completely, when 
the charging current is again turned on. This process is repeated 
over and over again, until the surfaces of the plates arc consider- 
ably attacked, one plate, however, being maintained in a state of 
oxidation. After a few days of this operation a period of rest is 
allowed between the reversals, which sols up a Local action on the 
oxidized plate, between the metallic lead of the plate, and its coat- 
ing of binoxide. This causes the lead to be attacked, under the 

influence of the local couple, and sulphate- of lead is formed, which, 
ultimately, by the charging current is converted into peroxide. 

These operations produce an exceedingly good battery. The pi 

ess described is termed forming. 

The plates separated by strips of insulating material arc generally 
wound into a double spiral. 

Battery, Siemens' and Halske's. A Daniel] battery of pecul- 
iar shape, 'flu- copper, ( ', is at the bottom of the glass jar, A. 

The inner jar, A', has the form of a bell, and supports a mass of 

paper pulp, which is dampened with sulphuric acia. The zinc, Z, 
rests on tap of the mass of pulp. The battery is very durable, 
but of high resistance. 

Battery, Sir William Thomson's. A form of Daniel! battery, 

of the gravity type. The receptacles are shallow wooden trays 
lined with lead. A thin plate Of COpper rests 

on the bottom. The zinc plate is of gridiron 
shape, and rests on wooden blocks which 
support it in a horizontal position above the 
copper. One tray is placed on top of the other, 

the upper tray resting on the corners of the 
zinc plate which rise above the level of the 
top of the flat vessel. Thus connection is 
assured without wires or binding posts. It i> 
charged like a gravity battery. The density 
of the zinc sulphate solution should he 
between i.ioand 1.30. The circuit must be 
kept closed to prevent deposition of metallic 
copper on the zinc. The entire disposition 
of the battery is designed to reduce resistance. 

Battery, Skrivanow. A pocket battery 
of the De la Rue type, with a solution of 75 Fig. 4 .. s.mee's Batteky. 




STANDARD ELECTRICAL DICTIONARY. 



part? caustic potash i;i too parts of water as the excitant. The 
silver chloride is contained in a parchment paper receptacle. Its 

electro-motive force is 1.45 to 1.5 volts. 

Battery, Smee's. A single fluid combination, with zinc 
positive plate, and a plate of silver, coated with platinum black, for 
the negative plate. The finely divided platinum affords a surface 
from which the hydrogen bubbles instantly detach themselves, 
thus preventing polarization. The liquid is a mixture of one part 
sulphuric acid to seven parts of water. For the negative plate 
silver-plated copper, coated with platinum black, is used. Electro- 
motive force, .47 volt. 

Battery, Spiral. A battery 
whose plates of thin zinc and cop- 
per are wound into a spiral so as to 
be very close, but not touching. 
Dilute sulphuric acid, is the excit- 
ant. It is now practically obsolete. 
ytonyms — Calorimeter — Hare's 
Deflagrator. 

Battery, Split. A battery of a 
number of voltaic cells, connected 
in series, with their central portion 
grounded or connected to earth. 
This gives the ends of opposite 
potentials from the earth, and of 
difference therefrom equal to the 
product of one-half of the number 
of cells employed, multiplied by 
their individual voltage. 

Battery Solutions, Chromic 

Acid. A number of formulae have Fig. 5* Spiral Battery, or Hare's 
been proposed for these solutions. Deflagrator. 

1 See Electropoion Fluid — Kookogcy's Solution — Poggendortps 
Solution — 7 You : >S y s Solution — Del a u rier's Sol ut ion — Ch uta ux*& 
Solution —Dronicr 's Salt —Tissandier' s Solution.) 

Battery, Trough. A battery whose elements arc contained in a 
trough, which is divided by cross-partitions so as to represent cups. 
rite wood for the trough is teak, which is divided by glass or 
slate partitions. Marine glue or other form of cement is used to 
make the joints tight. For porons enp divisions plates of porous 
porcelain or pottery are placed across, alternating with the imper- 
■ 

Battery, Trouve's Blotting Paper. A battery of the Daniel] 

□ which the solutions are retained by blotting paper. A con- 




74 



STANDARD ELECTRICAL DICTIONARY. 



siderable thickness of blotting paper lies between the two plates. 
The upper half of the thickness of the blotting paper is saturated 
with a solution of zinc sulphate, on which the zinc plate rests. 




i Battery, 

The lower half of the paper is saturated with copper sulphate 

solution, and this rests upon the copper plate. 

Battery, Tyer's. A modification, as regards the positive cle- 
ment, of Smec's battery, q. v. The bottom <>f the battery jar 




Fig. 52. Tver's Battery. 

contains a quantity of mercury in which pieces of zinc are thrown, 
and this constitutes the positive element. A ball of zinc at the end 



STANDARD ELECTRICAL DICTIONARY. 75 

of an insulated copper wire affords the connection with the zinc 

and mercury. Its great advantage is that the smallest scraps of 
line can be used in it, by being dropped into the mercury. The 
negative plate is platinized silver; the exciting liquid, dilute sul- 
phuric acid. 

Battery, Upward's. A primary voltaic cell, the invention of 
A. Reuec Upward. Referring to the cuts, the positive plate, Z, is 





Fig. 



Section of Urward's 
Battery. 



Fig. 54. Elevation of Upward's 
Battery. 



of cast zinc ; it is immersed in water, in a porous cup, B. Outside 
of the porous cup and contained in the battery jar are two carbon 
plates, C, C, connected together. The rest of the space between 
the porous cup and battery jar is packed with crushed carbon, and 
the top is cemented. Chlorine gas is led by a pipe, /), into the 
outer cell. It diffuses through the fine carbon, dissolves in the 
water, and so finds its way to the zinc, which it attacks, directly 
combining therewith, and forming zinc chloride (Zn + 2 CI Zn 
Such of the chlorine as is not absorbed finds its way by an 
outlet tube, E % to the next cell. Arrangements arc provided for 
generating chlorine gas as required. The high specific gravity of 
the gas is utilized in regulating its distribution through the cells. 
The electro-motive force of the cell is 2.1 volts. A cell II>£x5# 
ad 12 _' 2 inches dec]) has a resistance of 0.2 ohm. 

An overflow pipe, /*', with faucet, '/'. is supplied to withdraw the 
tion of zinc chloride aa it accumnlal 



76 STANDARD ELECTRICAL DICTIONARY. 

Battery, Varley's. A Daniell battery of the Siemens 1 and 

Halske's type (see Battery, Siemens' and Halske*s\ y in which zinc 
oxide is substituted for the paper pulp of the other battcrv. It 
has been very little used. 

Battery, Volta's. The original acid battery. It has a negative 

electrode of copper, a positive electrode of zinc ; the excitant is 
sulphuric acid diluted with sixteen times its volume of water. It 
rapidly polarizes, and is very little used. 

Battery, Voltaic or Galvanic. An apparatus for converting 

chemical energy directly into electric energy. This is as broad a 
definition as can well be given. The general conception of a 
battery includes the action of electrolysis, a solution in the battery 
acting upon one of two conducting electrodes immersed in such 
fluid, which dissolves one of them only, or one more than the 
other. The best way to obtain a fundamental idea of a battery ifl 
to start with the simplest. 1 dilute sulphuric acid dissolves neither 
pure zinc nor copper. But it lias a far Btronger affinity for the first 
named metal. If now we immerse in dilute acid two plato 
pure zinc, and one of copper, no action will be discernible. But if the 
plates arc brought in contact with each other a stream of bubbles 
of hydrogen gas will escape from the surface of the copper and the 
zinc will dissolve. By applying proper tests and deductions it will 
be found that the copper and zinc are being constantly charged with 
opposite electricities, and thai these are constantly recombining. 
This recombination produces what is known as an electric current. 

To constitute a battery the zinc and copper plates must be con- 
nected outside of the solution. This connection need not 
immediate. Any conductor which touches both plates will bring 
about the action, and the current will pass through it. 

The easiest way to picture the action of a battery is to accept the 
doctrine of contact action. In the battery the molecules of water 
are pulled apart. The hydrogen molecules go to the copper, the 
oxygen molecules go to the zinc, each one, leaving its contact 
with the other, comes off charged with opposite electricity. This 
charges the plates, and the continuous supply of charge and its 
continuous discharge establishes the current. 

The accumulation of hydrogen acts to stop the action by polari- 
zation. Its own affinity for oxygen acts against or in opposition 
to the affinity of the zinc for the same element, and so cuts down 
the action. A depolarizer of some kind is used in acid batteries 
for this reason. As such depolarizer has only to act upon one plate, 
inmost batteries it is usual to surround such plate only, as far as it 
is possible, with the depolarizer. The solution which dissolves the 
zinc is termed the excitant or exciting solution. 

To this concrete notion of a voltaic battery the different modifi- 
cations described here may be referred. Zinc, it will be seen, forms 



STANDARD KLKCTRICAL DICTIONARY. 



77 



the almost universally used dissolved plate; carbon or copper 
tonus the most usual undissolved plate ; sulphuric acid in one form 
or another is the most usual excitant. 

The solution in a voltaic battery is electrolyzed (see Electrolysis), 
Hence the solutions must be electrolytes. The sulphuric acid and 
other ingredients play a secondary role as imparting to the battery 
fluids this characteristic. 

It is not necessary to have electrodes of different substances, 
the same metal may be used for both if they are immersed indiffer- 
ent solutions which act differentially upon them, or which act with 
more energy on one than on the other. Such are only of theo- 
retical interest. 

Battery, Water. A voltaic battery, whose exciting fluid is 
water. 

They arc used for charging quadrant electrometer needles and 
similar purposes. They polarize very quickly and are of high 
resistance. Hence very small plates in large number can be used 
without impairing their advantage. 

Rowland's water battery dispenses with cups and uses capillarity 
instead. The zinc and platinum or copper plates of a couple are 
placed very close together, while the couples are more distant. 
On dipping into water each couple picks up and retains by capil- 
larity a little water between its plates, which forms the exciting 
fluid. Many hundred couples can be mounted on a board, and the 
whole is charged by dipping into water and at once removing 
therefrom. It then "develops its full potential difference. 



«*«_, 





OF WOLL^ 



. Plates ok Wol- 

LASTON'S UaTTKRY. 



78 STANDARD ELECTRICAL DICTIONARY. . 

Battery, Wollaston. The original plunge battery is attrib- 
uted to Wollaston. He also invented the battery known by his name, 
having the disposition shown in the cut, of zinc Z, surrounded by 
a thin sheet of copper C ; o, o' y o" , arc the terminals and />\ B x the 
battery jars. Dilute sulphuric acid is used for exciting fluid. 

B. A. U. Abbreviation for British Association unit, referring 
generally to the B. A. unit of resistance. 

B. A. Unit of Resistance. The original ohm used under that 
name previous to 1S84. The Paris committee of that year recom- 
mended as a practical unit what is known as the legal ohm. (Sec 
Ohm, Legal.) 

1 Legal Ohm 1.0112 B. A. Quits of Resistance. 

1 B. A. Unit of Resistance gal Ohms. 

44 .9865] < io* C. G. S. units. 

B. E. adj. Britisli Engineering, a qualification <>f a set of units, 

the B. K. units, having fir base the foot and pound. The term is 
but little used. 

Beaume Hydrometer. A hydrometer graduated on the follow- 
ing principle: 

The zero point Corresponds to the specific gravity of water for 
liquids heavier than water. A solution of 15 parts <>f salt in S5 
parts of water corresponds in specific gravity to 15 B., and between 
that and zero fifteen equal degrees are laid out. The degn 
carried down below this point. 

The zero 'points for Liquids Lighter than water correspond to the 
specific gravity of a solution of eo parts of salt in 90 parts of water. 
The specific gravity of water is taken as io° B. This gives ten 
degrees which are continued up the scale. 

Becquerel's Laws of Thermoelectricity. These are stated 
under the heads, Law of Intermediate Metals and Law ofSuco 

Temperatures, q. v. 

Bed Piece. In a dynamo or motor the frame carrying it, includ- 
ing often the standards in which the armature shaft is journalcd, 
and often the yoke or even entire field magnet core. 

Bell, Automatic Electric. A bell which rings as long as the circuit 
is closed, having a circuit breaker operated by its own motion. (See 
Bell y Eleclric.) 

Synonyms — Trembling Bell— Vibrating Bell. 

Bell, Call. A bell operated by electricity, designed to call 
attention, as to a telephone or telegraphic receiver. (See Bell, 
Electric,) 



STANDARD ELECTRICAL DICTIONARY. 



79 



Bdl Call. A calling device for attracting the aucntion of any 
one, consisting of some type of electric belL 

Bell, Circular. A gong-shaped bell, whose clapper and general 
mechanism is within its cavity or behind it. 

Bell, Differentially Wound. An electric bell, whose magnet is 
wound differentially so as to prevent sparking. 

Bell, Electric. A bell rung by electricitv. Generally it is 
worked by a current exciting an' electro-magnet, attracting or 




Fig 57. Automatic Electric Bi 
releasing an armature which is attached to the vibrating or pivoted 
tongue of the bell. It may be worked by a distant switch or press- 



80 vSTANDARD ELECTRICAL DICTIONARY. 

button, q. v., ringing once for each movement of the distant switch, 
etc., or it may be of the vibrating bell type as shown in the cut. 
When the current is turned on in this case it attracts the armature. 
As this moves towards the poles of the magnet it breaks the circuit 
by drawing the contact spring, q. v., away from the contact point, 
q. v. This opens the circuit, to whose continuity the contact of 
these two parts is essential. The hammer, however, by its momen- 
tum strikes the bell and at once springs back. This again makes 
the contact and the hammer is rcattractcd. This action continues 
as long as the circuit is closed at any distant point to which it may 
be carried. The ordinary vibrating bell is a typical automatic 
circuit breaker, q. v., this type keeping up the ringing as long 
as the circuit is closed. Other bells have no electric contact and 
simply ring once every time the circuit is closed. ( Hhcrs worked 
by an alternating current ring once for each change of direction of 
current. 

Bell, Electro=mechanical. A bell which has its striking train 
operated by a Spring or descending weight, and which tram is 
thrown into action by the release of a detent <>r equivalent action 
by the closing of an electric circuit. It rings for any given time 
after being started. 

Bell, Indicating. A bell which by drop-shatter or other indica- 
tor connected in circuit with it, indicates its number or other desig- 
nation of its call. 

Bell, Magneto. An electric bell operated by the alternating 
current from a magneto generator. It has a polarized armature 
and no circuit breaker. The armature is attracted first m one direc- 
tion and then in the other, as the current alternates and reverses 
the polarity of the electro-magnet. 

Bell, Relay. A bell operated by a relay circuit. 

Bias. In polarized relay the adjustment of the tongue to lie 
normally against one or the other contact. (See Relay, Pola> 




fa e- 



Fig. 58. Resistance Coils Showing Bifilar Winding. 



STANDARD KLECTRICAL DICTIONARY. 



Si 



Bifilar Winding. The method followed in winding resistance 
coils to prevent: them from creating fields of force. The wire is 
doubled, and the doubled wire starting with the bend or bight is 
wound into a cod. The current going in opposite senses in the 
two lavs of the winding produces no field of force. 

Binary Compound. A chemical compound whose molecule con- 
tains only two elements, such as water (H._, O), lead oxide (Pb O), 
and many others. 

Binding. In a dynamo or motor armature the wire wound 
around the coils to secure them in place and prevent their disturb- 
ance by centrifugal action. 

Binding Posts or Screws. Arrangements for receiving the 





wmm 







Fig. 59. Double Binding Post. 






Fig. 60. Binding Post, 
English Pattern. 




Fig. 61. Wood 

Screw Binding 

Post. 



loose end of a wire of an electric circuit, and securing such end by 
a screw. Several constructions are used, as shown here. Some- 
times the wire is passed through a hole, and a screw tapped in at 
right angles to the hole is screwed down upon the wire. Some- 
times the wire is clamped between two shoulders, one on the screw, 
the other on the post. The screw is often a flat-headed thumb 
screw or has a milled edge. Sometimes the screw has a slot and is 
turned by a screw-driver. 

ral openings are often provided in the same post for different 

Binnacle. The case containing a mariner's compass on ship- 
1 completely ; it has a glass side- or window 

gh which the compass can be seen, and is provided with one 



82 



STANDARD ELECTRICAL DICTIONARY. 



or two lamps arranged to light the card, while showing as little 
light as possible outside. 

Bioscopy, Electric. The diagnosis of life and death by the 
action of the animal system when subjected to an electric current 
or electrification. 

Bismuth. A metal, one of the elements, atomic weight, 210 ; 

equivalent, 70 ; valency, 3 ; specific gravity, 9.9. It is a conductor 
of electricity. 

Relative Resistance, com presse d, [silver 1 ^7.2; 

vSpccific Resistance-, [31.2 microhms 

Resistance of a wire 
(a) 1 foot long, weighing t grain, 5-054 ohms 

lb) 1 foot long, 1- 1000 inch thick, 7890 

(r) [ meter long, weighing 1 gram, 5 M 

(a) [meter long, r millimeter thick, 1.670 M 

Resistance ofa [-inch cube 51.65 microhms 

Electrochemical equivalent, >735<> 

(Hydrogen .0105) 
(Sec Thermoelectric Si > 




Figs. 62, 63. 
Fuse. 




Incandescent Wire 

Abel's Pa i > 



Fig. 64. Von Ebner's Frictional 1 
tric Machine for Exploding Electric 
or Detonators. 

Bi=telephone. A pair of telephones arranged with a curved con- 
necting arm or spring, so that they can be simultaneously applied 
to both ears. They are self-retaining, staying in position without 
the use of the hands. 



STANDARD ELECTRICAL DICTIONARY, 83 

Blasting, Electric. The ignition of blasting charges of powder 

or high explosives by the electric spark, or by the ignition to 
incandescence (red or white heat) of a thin wire immersed in or sur- 
rounded by powder. Special influence or frictiona] electric 
machines or induction coils are used to produce sparks, if that 

method of ignition is employed. For the incandescent wire a hand 
magneto is very generally employed. (See Fuse t Electric,) 

The cuts, Figs. 62 and 63, show one form of incandescent wire fuse. 
The large wires are secured to the capsule, so that no strain can 

come upon the small wire within the cavity. 

The cut, Fig. 64, shows a frictional electric machine for igniting 
spark fuses. 

Bleaching, Electric. Bleaching by agents produced or made 
available by the direct action of electricity. Thus if a current 
under proper conditions is sent through a solution of common salt 
f sodium chloride), the electrodes being close together, the salt is 
decomposed, chlorine going to one pole and sodium hydrate to the 
other. The two substances react upon each other and combine, 
forming sodium hypochlorite, which bleaches the tissue immersed 
in its solution. 

Block System. A system of signalling on railroads. The 
essence of the system consists in having signal posts or stations all 
along the road at distances depending on the traffic. The space 
between each two signal posts is termed a block. From the signal 
posts the trains in day time are signalled by wooden arms 
termed semaphores, and at night by lanterns. The arms may be 
moved by hand or by automatic mechanism depending in part on 
electricitv for carrying out its functions. Thus in the Westinghouse 
system the semaphores are moved by pneumatic cylinders and 
pistons, whose air valves arc opened and shut by the action of sole- 
noid magnets, q. v. The current of these magnets is short circuited 
by passing trains, so as to let the valves close as the train passes 
the signal post The block system causes the semaphore to be set 
at "danger' 1 or "caution," as the train enters the next block. 
Then the following train is not allowed to enter the block until 
the safety signal is shown. The Westinghouse system pro- 
vides for two semaphores on a post, one indicating u danger " as long 
as the train is on the next block ; the other indicating " caution M 
as long as the train is on the next two blocks. The rails form part 
of the circuit, their joints being bridged by copper wire throughout 
the block, and being insulated where the blocks meet. 

Block Wire. In the block system a wire connecting adjacent 
block-signal to- . maphore poles. 

Blow -pipe. A name Bonn tinu - given t<> an electric experiment 

illustrating the repulsion of electrified air particles from a point 



84 vSTANDARD ELECTRICAL DICTIONARY. 

held at high relative potential. A metallic point, placed on the 
prime conductor of an electric friction or influence machine, 
becomes highly electrified, and the air becoming excited is repelled 
and acts upon the candle flame. If the candle is placed on the 
conductor and a point held towards it the repulsion is still awav 
from the point. 

Blow=pipe, Electric Arc. A name sometimes given to d< 
for using the voltaic arc to produce local heating effects. The 

directive action of the magnet may be used to force out the arc 
like a blow-pipe flame, or a blast of air may be directly applied for 
the same purpose. 

Blue=stone. A trade name for crystallized copper sulphate, 

used in DanielTs and gravity batter 

Boat, Electric. A boat propelled by electricity. The 

trieity drives a motor which actuates :i screw propeller. The cur- 
rent is generally supplied by a Storage battery. When used on 

rivers charging stations arc established at proper places. When 
the boat is. used asa tender or launch for a steam ship, such as a 
war-vessel, the battery is charged by a plant on board the ship. 
From their noiselessm ^s electric boats are peculiarly available for 
nocturnal torpedo operations, and the universal equipment of 

modern war-ships with electric lightning and power plants makes 

their use possible at all points. Phis type is often termed an elec- 
tric- launch, and most or all electric boats fall under this category. 

Bobbins. A. Spool of wood or other material wound with insu- 
lated wire, in a tangent galvanometer the bobbin becomes a ring, 
with a channel to receive the winding. As the- ring is not infinitely 
large compared to the needle the tangent law is not absolutely ful- 
filled. It is most accurately fulfilled ^S. P. Thomson) when the 
depth of the groove or channel in the radial direction bears to the 
breadth in the axial direction the ratio of 

I 'a : i i or approximately 11:9 

Body Protector. A metallic short circuit connected with the 
wrists and lower legs of the human body , so that if by accident 
an active circuit is grounded by the hands and body of the workman 
wearing it, most of the current will pass through the wire con- 
ductors, thus avoiding the vital organs of the body. 

Boiler Feed, Electric. An apparatus by which an electric cur- 
rent acting on an electro-magnet, or other equivalent device, 
opens the water supply when the water level in a boiler sinks too 
low, and cuts off the water supply as the water level rises. 

Boiling. In secondary batteries the escape of hydrogen and 
oxygen gas when the battery is charged. The bubbling of the 
escaping gases produces the effect of boiling. 



STANDARD ELECTRICAL DICTIONARY. S5 

Boll. An absolute or c. g. s. t unit of momentum ; a gram mov- 
ing at the rate of one centimeter per second ; a gram-kine (see 
; a unit proposed by the British Association. 

Bolometer. An apparatus for detecting small amounts of 
radiant energy 1 radiant heat, so called . A coil suspended by a 

fine wireor rilamcntsoasto be free to rotate under the effect of force 
is made up of two parallel and equal wires, insulated from each 
other, but connected so that parallel currents sent through them 
go in opposite direction through each. This coil is hung in a 
strong electro-magnetic field produced by a large coil surrounding 
it. When a current passes through the suspended coil no effect 
will follow, because the oppositely wound portions counteract each 
other exactly. In the circuit with one half of the suspended coil 
is an exceedingly thin strip of platinum wire. The other half of 
the coil has no strips. Both halves unite after leaving the coil. 
If now the strip of platinum is heated its conductivity is affected 
and its half of the coil receives less current than the other half. 
This disturbs the balance and the coil swings through a small arc. 
This apparatus may be made very sensitive, so that an increase 
of temperature of 1-25200 °C. (1-14000 °F.) will be percep- 
tible. Another construction takes the form of a Wheatstoue 
Bridge, q. v., in whose arms are introduced resistances consisting 
of bands of iron, .5 millimeter wide (.02 inches), .004 millimeter 
(.00016 inch) thick, and folded on themselves 14 times so as to 
make a rectangular grating, 17x12 millimeters (.68 x .48 inch). 
The least difference of heat applied to the grating affects the gal- 
vanometer. 

nytn — Thermic Balance. 

Boreal Pole. The south pointing pole of the magnet. (See 
. iustral Pole 1 

Bot. A colloquial expression for the English Board of Trade 
unit of Electrical Supply. It is formed of the initials of the words 
M Board of Trade.'' (Sec Unit, Board of Dade.) 

Box Bridge. A construction of Wheatstone's Bridge in which 

the necessary resistance coils are contained in a single box with 

plugs for throwing the coils in and out of circuit, and connections 

to bring the coils into the different arms of the System. The cut 

a box bridge. Connections for the galvanometer, battery 

and terminals of the unknown resistance .arc provided, by 

which its r - and the connections are brought into the 

in the conventional diagram ofWheat- 

// in al stone" 5 Bridi 

Referring to the cut, the battery wire, say from the zinc plate, 

& % thereby reaching A^ its true connecting point. To 

A 1 one end of tl; ait or had is attached, thereby 



86 



STANDARD ELECTRICAL DICTIONARY. 



reaching B, its true connecting point. To C arc connected the 
other end from the galvanometer and one end of the unknown 




Fig, c I 



Box B 



resistance. The other end of the unknown resistance, and the 

oilier end of the battery wire, inthiscase from the carbon plate, 
connect to P. At G isan infinity ping, as it is called, Wh< 

it breaks the circuit. B and E are connected by B copper plate. 

In use after the connections are made the key is depressed and 

the galvanometer observed. The resistance is changed until no 
action of the galvanometer is produced by closing the circuit when 
the ratio of the resistances of the arms gives tine proportion for 

calculating the unknown resistam 

Synonym — Commercial Wheatstone I .ridge, or commercial form 
of same. 

Boxing the Compass. Naming the thirty-two points of the 
compass in order, and in sequence to any point called out at ran- 
dom. There arc many exercises in the relative sailing points and 
bearings that come under the same head. Thus the direction of 
two given points being given by names of the compass poims, it 
may be required to state the number of points intervening. 

Brake, Electro=magnetic. A brake to stop a wheel from 
rotating. It comprises a shoe, or sometimes a ring, which by 
electro-magnetic attraction is drawn against the rotating wheel, 
thus preventing it from turning, or tending to bring it to rest. (Sec 
Electro-magnet, Annular*} 



STANDARD ELECTRICAL DICTIONARY. 



87 




Fig. 66. Electric Brake. 

Branch. A conductor branching from a main line. Sometimes 
the term is restricted to a principal conductor, from which current 
is distributed. 

Branch Block. In electric wiring of buildings, a block of 
porcelain or other material with grooves, holes and screws for the 
connection of branch wires to a main wire. Its functions are not 
only to afford a basis for connecting the wires, but also to contain 
safetv fu^cs. As when a branch wire is taken off, fuses have to be 
put in its line, the branch block carries these also, One end of 
each fuse connects with a main wire, the other end connects with 
one of the wires of the branch leader or wire. 

Porcelain is a favorite material for them, as the fusing or "blow- 
it "of the safety fuses cannot set it on fire. 

Branch Conductor. A parallel or shunt conductor. 

Brazing, Electric. Brazing in which the spelter is melted by 
means of electricity; either current incandescence or the voltaic 
arc may be used. It is identical in general with electric welding. 
See // 'elding , Elei 

Branding, Electric. A system of branding in which the fa 
electrically ignited or incandescent conductors is used to produce 

or burn in the marks upon the- surface. For the alternating current 

U transformer is connected to or forms part of the tool. 

Brassing. TJie deposition of a coating of brass by electro! 
The plating bath \ both copper and /:;)«■ As anode a plate 



88 STANDARD ELECTRICAL DICTIONARY. 

of brass is used. The operation must be constantly watched. 
The deposition of both metals goes on simultaneously, so that a 
virtual alloy is deposited. By changing the depth of immersion of 
the anode the color of the deposit is varied. 

As a formula for a brassing bath the following arc typical. They 
are expressed in parts by weight. 

(a) For iron and steel. 

I. 

Sodium Bisulphate, 200 
Potassium Cyanide, 70 per cent., 500 

Sodium Carbonate, 1,000 

Water, .\ooo 

II. 

Copper Acetate, 125 

Zinc Chloride, too 

Water, 2,000 

Add the second solution to the first. 

(b) For /inc. 

I. 
Sodium Bisulphate, 700 

Potassium Cyanide, 70 per cent., 1,000 
Water, .000 

II. 
Copper Acetate, 
Zinc Chloride, 
Aqua Ammonia , 

Water, 5>OO0 

Add the second solution to the first 

Use a brass anode ; add more zinc to produce a greenish color ; 

more copper for a red color. A weak current gives a red color ; a 
strong current lightens the color. The battery power can be 
altered, a larger or smaller anode can be used, or a copper or zinc 
anode can be used to change the color of the deposit. The bath 
may vary from 1.036 to 1. 100 sp. gr., without harm. 

Break. A point where an electric conductor is cut, broken, 
or opened by a switch or other device, or simply by discontinuity 
of the wires. 

Break=down Switch. A switch used in the three-wire system 
to provide for the discontinuance of the running of one of the 
dynamos. 

By connecting the positive and negative bus wires to one terminal 
of the active dynamo, and the neutral bus wire to the other terminal, 
one dynamo will supply the current and the system operates like a 
two-wire system, but can only be used for half its normal capacity. 



STANDARD ELECTRICAL DICTIONARY. S 9 

Breaking Weight. The weight which, applied in tension, will 
break a prism or cylinder, as an electric current conductor. 

Breath Figures, Electric. If a conductor is electrified and 
placed upon a piece of glass, it will electrify the glass in contact 
with it by conduction or discharge. On removing the conductor 
the glass remains electrified. The localized electrification is shown 
by breathing gently on the glass, when a species of image of the 
conductor is produced by the condensed moisture. A coin is often 
used for conductor. 

Breeze, Electric. A term in medical electricity, used to desig- 
nate the silent or brush discharge of high tension electricity. As 
an instance of its employment, the electric head bath (see Baih % 
Electric I lead, \ may be cited. The patient forming one electrode, 
being insulated and connected to one of the conductors, the other 
conductor, on being brought near his person, discharges into his 
body. 

Bridge, a A special bar of copper connecting the dynamos to 
the bus wire, q. v., in electric lighting or power stations. 

Wheatstone's bridge, q. v., and its many modifications, all 
of which may be consulted throughout these pages. 

British Association Bridge. The type of Wheatstone bridge 
used bv the committee of the association in determining the B. A. 
ohm ; the meter bridge, q. v. 

Broadside Method. A method of determining 
the magnetic moment of a magnet. The magnet, 
//, Sj under examination is fixed so that it is at right 
angles to the magnetic meridian, J/, A\ which passes 
through its own center and that of a compass needle. 
From the deflection of the latter the moment is 
calculated. 

Bronzing. In electro-plating the deposition of 
a mixture or virtual alloy of copper and tin. In 
general manipulation it resembles the operation of 
depositing gold and silver alloy, or of brassing. 
For bronzing the following bath is recommended: 
Prepare each by itself (a) a solution of copper 
phosphate and {&) a solution of stannous chloride 

in a solution of sodium pyrophosphate. For 0, 

c recently precipitated copper phosphate in 

titrated solution of sodium pyrophosphate. 

For b t add to a saturated solution of sodium pyro- 
ph i tuition of stannous chloride as long as 

the precipitate which is formed dissolv< s. Of these two solutions 
add to a solution of sodium pyrophosphate which contains about 





90 STANDARD ELECTRICAL DICTIONARY. 

1% oz. of the salt to the quart, until the precipitate appears 
quickly and of the desired color. For anodes use cast bronze 
plates. Sodium phosphate must be added from time to time ; if 
the deposit is too light add copper solution, if too dark add tin 
solution. (W. T. Brannt.) 

Brush. In electric current generators and motors, the pi© 
copper or other material that bear against the cylindrical surface 
of the commuU tor arc thm ermed. Many different constructions 
have been employed. Some have employed little wheels or <1. 
bearing against and rotating on the surface of the commutator. 
A bundle of copper strips is often employed, placed flatwise. 
Sometimes the same are used, but are placed edgewise. Wire in 
bundles, soldered together a L their distant ends have been employed. 
Carbon brushes, which are simply rods or slabs of carbon, arc used 
with much success. 

Synonym Collecting Brush. 

Brush, Carbon. A brush for a dynamo or motor, which con- 
sists of a plate or rod of carbon, held in a brush holder and pressed 
against the commutator surface. 

Brushes, Adjustment of. In electric current generators and 
motors, the brushes which bear upon the- commutator when the 
machine is in action need occasional adjustment. This is effected 
by shifting them until sparking between them and the commutator 
is nearly or quite suppressed. 




Fig. 68. Brush Holder. 
Brushes, Lead of. In a dynamo electric generator, the lead 
or displacement in advance of or beyond the position at right angles 
to the line connecting the poles of the field magnet, which is given 
the brushes. In a motor the brushes are set back of the right 
angle position, or are given a negative lead. ^Sce Lag.) 



STANDARD ELECTRICAL DICTIONARY. 



91 



Brush Holders. The adjustable (generally) clutch or clamps for 
holding the commutator brushes of a dynamo, which keep them in 
contact with the commutator, and admit of adjustment by shift- 
ing backward and forward of the brushes to compensate for wear. 
They arc connected to and form part of the rocker, q. v. By rotat- 
ing the latter the brush-Holders and brushes are carried in one 
direction or other around the commutator, so as to vary the lead as 
required. 

Brush, Pilot. A third brush, used for application to different 
parts of a revolving armature commutator to determine the distrib- 
ution of potential difference between iU different members. (See 
Curie of Distribution of Potential in Armature*} One terminal 




Fig. 69. Pilot Brush. 



of a volt-meter is connected to one of the regular brushes, A y of a 
dynamo; the other to a third brush, />, which is pressed against 
different portions of the commutator of the dynamo. The read- 
ings of the volt-meter are plotted in a curve of distribution of 
potential. 

Brush, Rotating. Brushes for taking off the current from 
dynamo commutators, or giving current connection to motors, 
whose ends are in the form of rollers which rotate like little wheels, 
and press against the commutator surface. 

Brush, Third. A third brush is sometimes provided in a dyna- 
mo for regulating purposes. Applied to a series machine it adjoins 

<>ne of the regular brushes and delivers its current to a resistance, 

to whose further end the regular circuit is connected. By a sliding 
connection the resistance is divided between the third brush circuit 



9 2 



STANDARD ELECTRICAL DICTIONARY. 



and the regular circuit, and by varying the position of this contact 
regulation is obtained. 




Fig. 



TlUKI- I : HION. 



It is to be distinguished from the pilot brash used for determining 

the characteristic of the commutator, although based on the same 

general principles. 

Brush, Wire Gauze. A collecting or commutator brush for 

a dynamo or motor, which brush is made of wire- gauze rolled up 
and compressed into shape. 

Buckling. The bending up and distortion of secondary battery 
plates. It is Largely due to over-exhausting the batteries. Where 

the E. M. F. is never allowed to frill below I.90 volt it is far less 
liable to occur. 

Bug. Any fault or trouble in the connections or working of 
electric apparatus. 

Bug Trap. A connection or arrangement for overcoming a 
11 bug." 

It is said that the terms "bug" and "bug trap" originated in 
quadruplex telegraphy. 

Bunsen Disc. In photometry, the Bunsen Disc is a piece of 
paper upon whose centre a Spot is saturated with melted paraffin, 
or a ring of paraffined surface surrounds an untouched central spot 
If placed in such a position that it receives an equal illumination 
on each side, the spot almost disappears. It is used on the bar photo- 
meter. (See Photometer, Bar.) 

Synonym— Grease Spot. 



STANDARD ELECTRICAL DICTIONARY. 93 

Buoy, Electric. A buoy for use to indicate channels or dangers 

In harbors and elsewhere, which carries an electric light, whose 
current is supplied by cable from shore. It has been proposed to 
use glass tubes exhausted of air and containing mercury, which, as 
moved by the waves, would produce a luminous effect. A fifty- 
candle power incandescent lamp is an approved source of light. 

Burner, Electric Gas. A gas burner arranged for the flame to 

be lighted by electricity. It takes a great variety of forms. In 
some cases a pair of terminals are arranged near the flame or a 
single terminal is placed near the metal tip, the latter forming one 
of the terminals. The spark is generally produced by an induction 
coil, or a spark coil. The gas may first be turned on and the spark 
then passed. Sometimes the turning of the gas cock of an indi- 
vidual burner makes and breaks a contact as it turns, and thereby 
produces simultaneously with the turning on of the gas a spark 
which lights it. 

Another form is wholly automatic. A pair of electro-magnets 
are attached below the base of the burner, one of which when 
excited, turns on the gas, and the other one when it is excited turns 
it off. At the same time a spark is produced with the turning on of 
the gas so that it is lighted. Thus, by use of a automatic burner, a 
distant gas burner can be lighted by pressing an electric button. 
An out-door lamp may be lighted from within a house. 

The increasing use of electric incandescent lamps, lighted by the 
turning of a switch, tends to displace electric gas burners. The 
latter have been classified into a number of types depending on 
their construction. 

Burners are sometimes connected in series with leads from an 
induction coil. Then the gas is turned on all at once, and a suc- 
cession of sparks passed until the gas is ail lighted. The ignition 
is practically instantaneous. 

Button, Push. A species of switch which is actuated by the 
pressure of a button. In its normal posi- 
tion the button is pressed outwards by a 
spring, and the circuit is open. When 
pressed inwards, it closes the circuit. 
When released it springs backward and 
opens the circuit again. 

They are principally used for ringing 
bells. " If the latter are of the automatic 
type, they ring as long as the button is 
pressed. 

For door-bells and room-bells, the button 
often occupies the- center of a rosette of 
wood or bronze or other ornamental piece. 
Fig. 71 Floor Push Button. Sometimes, as shown in the cut, the} arc 




94 



STANDARD ELECTRICAL DICTIONARY. 



constructed for use on floors to be pressed by the foot. The general 
principle of their construction is shown, although the method of 
making the contact varies. 
Synonym — Press Button. 

Burning, (a) In a dynamo, the production of shifting and 
temporary arcs between the commutator and brushes, which arcs 
produce heat enough to injure the parts in question. 

(b) In electro-plating, a defect due to too strong a current in 
proportion to the strength of solution and area of electrodes. This 
gives a black or badly-colored deposit. 

Bus Rod. A copper conductor used in electric lighting or 
power stations, to receive the current from all the dynamos. The 
distributing leads are connected to the bus wires. 

In the three-wire system there are three ; in the- two-wire system 
there arc two bus wires. 

The name is undoubtedly derived from " omnibus." 

The bus wires may be divided into positive, negative, and, in the 
three-wire system, neutral bus wir- 

Synonyms Omnibus Rod, Wire-, or Bar Bus Bar, or Wire. 

Buzzer. An electric alarm or call produced by B rapid vibration 
of electric make and break mechanism, which is often magnified 




Fig. 72. Buzzer. 

by enclosure in a resonating chamber, resembling a bell, but which 
is not struck or touched by the vibrating parts. Sometimes a 
square wooden box is used as resonator. 

B. W. G. Abbreviation for Birmingham Wire Gauge. (Sec 
Wire Gauge \ Birmingham.} 



STANDARD ELECTRICAL DICTIONARY. 95 

C. a Abbreviation for Centigrade, as.io° C, meaning [o° Centi- 
grade. (See Centigrade Scale.} 

\b\ A symbol o\ current or of current strength. Thus in the 
expression of Ohm's law C E R, C indicates current strength or 
intensity, not in any fixed unit, but only in a unit of the same 
order in which K and R are expressed ; I\ indicating electro-motive 
force and R resistance. 

Cable, [a] Abbreviation for Cablegram^ q. v. 

[b) :•. It is also used as a verb, meaning to transmit a message 
by submarine cable. 

[c). An insulated electric conductor, of large diameter. It 
often is protected by armor or metallic sheathing and may be 
designed for use as an aerial, submarine, subterranean or conduit 
cable. A cable oftens contains a large number of separately insu- 
lated conductors, so as to supply a large number of circuits. 

Cable, Aerial. A cable usually containing a large number of 
separately insulated wires, and itself insulated. It is suspended 
in the air. As its weight is sometimes so great that it could 
not well sustain it, a suspending wire is in such cases carried 
along with it, to which it is suspended by cable hangers, q. v. 

Cable Box. A box for receiving underground cable ends and 
connecting the separate wires of the cable to air-line wires. It is 
often mounted on a pole, which forms the starting point of the 
air-line portion of the system. 

Cable, Bunched. A cable containing a number of separate and 
individual conductors. In some forms it consists virtually of 
two or more small cables laid tangent to each other and there 
secured. Thus each in section represents two or more tangent 

circles with the interstice solidly filled with the metal sheathing. 

Cable, Capacity of. The electrostatic capacity of a cable. A 
cable represents a Lcydcn jar or static condenser. The outer 
sheathing or armor, or even the more or less moist coating, if it 
is unarmorcd, represent one coating. The wire conductors repre- 
sent the other coating, and the insulator is the dielectric. 

The capacity of a cable interferes with its efficiency as a con- 
ductor of broken or interrupted currents, such as are used in teleg- 
raphy or telephoning. As each impulse or momentary current is 
sent into the line, it has to charge the cable to at least a certain 
extent before the effects of the current are perceptible at the other 

end. Then the cable- has to discharge itself. All this creates a 

drag or retardation. 

The capacity of a cable is caed to determine the locality of 

breaks in the continuity of the conductors. The capacity per 
unit of length being accurately known, it is obvious that, if the 



96 



vSTANDARD ELECTRICAL DICTIONARY. 



conductor breaks without disturbance of the insulator, the distance 
of the break from the end can be ascertained!)}' determining the 
capacity of the cable from one end. This capacity will be in pro- 
portion to the capacity of a mile, a knot or any fixed unit, as the 
distance to the break is to the length used as standard. 

Cable Core. The conductors of a cable. They arc generally 
copper wire. In a telephone cable they may be very numerous 
and insulated from each other. In ocean cables they may be a 
group of bare wires twisted or laid together. Sometimes the 
conductors arc arranged for metallic circuits, each pair being dis- 
tinguished by special colored windings. 

Cable, Duplex. A cable containing two wires, each with separate 

insulation, so as to be virtually two cables, laid and secured parallel 

and side by side. 

Cable, Flat. A cable, flat in shape, so as to lie closely against a 
wall or ceiling. 

Cablegram. A message which has been transmitted or is to be 

transmitted by a submarine cable. It is sometimes called a cable. 

Cable Grip. A grip for holding the end ofa cable, when the 
cable is to be drawn into a conduit in a subway. It is an attach- 
ment to provide the cable with an eye or loop. Its end is a split 

socket and embraces the cud of the cable-, and 18 Secured thereto by 
bolts driven through the cable end. In drawing a cable into a 
conduit a capstan and rope are often used, and the rope is secured 
to the cable end by the grip. 





Fig. 73- 



Cable Hangf.r, Cable, and Sus- 
pending Wire. 



Fig. 74. Cable Hanger, 
Open. 



Cable Hanger. When a heavy electric cable is suspended from 
poles it often would be unsafe to trust to its longitudinal strength to 
support or sustain its own weight unless the poles were very near 
together. In such case an auxiliary or sustaining wire is run along 



STANDARD ELECTRICAL DICTIONARY 97 

with it, and by dips or hangers the cable is connected thereto at 
as frequent intervals as seem desirable. The contrivance may 
take the form of a strip of metal surrounding the cable and carry- 
ing a hook or eye through which the supporting wire passes. 
Synonym- Cable Clip. 

Cable Hanger Tongs. Tongs for attaching cable hangers, q. v. 
Thev have long handles so as to be worked from the ground at the 

middle of a span. 

Cable, Suspending Wire of. A wire by which an aerial cable 
is in part or entirely suspended. The cable, being incapable of sus- 
taining its own weight, is secured by clips or hangers to a wire, 
strung from pole to pole immediately above it. (See Cable 

Cable Tank. A tank in which a submarine cable is coiled away 
onboard a cable-laying ship, or in the factory on shore for the pur- 
pose of testing or watching its insulation. Sometimes, in order to 
test it under pressures approximating to those it will be subjected to 
in practice, the tank is closed and the portion of cable within it is 
subjected to hydraulic pressure. This represents the pressure it 
will be exposed to in deep water. 

Calamine. A mineral ; zinc silicate; formula Zn 2 Si 3 , crystalline 
system, Orthorhombic ; specific gravity, 3.16— 3.9. 

The crystals often show strong pyroelectric properties. 

Calibration. The determination by experiment or calculation 
of the value of the readings of an instrument, such as a galva- 
nometer or eudiometer. Thus if a tangent galvanometer has 
its circle graduated in degrees, a table of the value of tangents 
corresponding to every reading occurring in practice would repre- 
sent a calibration by calculation. A determination of the current 
required to produce each deflection would be a calibration in the 
more usual sense. Calibration is generally absolute, as referring 
to some fixed unit, but it may be relative, as between two things 
both of unknown absolute value. 

Calibration, Absolute. The determination of the absolute 
value of currents producing given deflections in a galvanometer, or 
in other instruments the determination of corresponding values, as 
the instrument may be a magnetometer, quadrant electrometer, or 
other appai 

Calibration, Invariable. Calibration applicable to specially 
constructed galvanometers, which is unaffected by the proximity of 
masses of iron or field magnets. Such galvanometers must have a 

nt controlling field. Such is given by a powerful permanent 

magnet, whose field is practically unaffecu d by tin- causes named. 



98 



STANDARD ELECTRICAL DICTIONARY. 



Or else, in place of a controlling field, a spring maybe used to which 
the needle is attached, and which tends to hold it in one position. 

Calibration, Relative, The determination of the law connect- 
ing the various indications of an instrument, such as the deflec- 
tions of the needle of a galvanometer, with the relative causes ; in 
the case of a galvanometer, the strength of the currents or the 
electro-motive forces producing them directly or indirectly. 

Call Bell. A bell rung by pressing a b therwise * 

the attention of a person in a distant place. They can he classified 
into a great variety of types according to their instruction. 

Call Button. A push button used for ringing a call hell, sound- 
ing a buzzer, working an annunciator and for similar pur] 

(Sec- Push Button, | 
Synonym Push Button. 

Calling Drop. In ;i telephone exchange or telegraph oflG 
drop shutter annunciator, which Tails to call the attention of the 
operator, notify ing him that the lin< 1 to such dr<>]> i*, to be 

connected to some other circuit 

Calorie or Calory. A practical unit irf heat. There are two 
calories, respectively called tin- great and the small calorie, or the 
kilogram and tfa calorie, 'flu- first is the quantity of heat 

required to rais t - the temperature of one kilogram of water one 
decree centigrade. The second is the* quantity of heat required to 
raise the temperature- of one gram <>f water one degree centigrade. 

Calorimeter. An apparatus tor measuring the- quantity of heat 
evolved or produced by or under 
different conditions. Dulong's water 
calorimeter consists of a water jacket, 

and by the- increase- of temperature 
of the water and enclosing vessels 
the- amount of heat produced by 

anything in the inner vessels is deter- 
mined. The amount of ice a heated 
body will melt is sometimes made 
the basis of a calorimeter. The ex- 
pansion of a fluid, as water, may 
be nsed. In the calorimeter shown 
in the cut the heat produced in a 
conelnctor hv the passage of an elec- 
tric current is caused to heat water 
whose temperature is shown by a 
thermometer immcrseel therein. The 
increase of temperature and the 
Fig - . 75- Calorimeter. weight of the water give the basis for 




STANDARD KI.KCTRICAI. DICTIONARY. 99 

a determination of the heat produced by the current. Knowing 
the resistance ot the conductor immersed, the watts can be cal- 
culated. This gives the bases for the determination of the heat- 
equivalent of electric energy. This is but an imperfect calorimeter, 
as it constantly would Lose heat by the surrounding atmosphere, 
and would cease to operate as a calorimeter when the water was 
as hot as the wire normally would be, for then it would not absorb 
all the heat. 

Candle. The generally accepted unit of illuminating power ; 
there are three kinds in use as standards. (See Candle y Decimal — 
La ;/ die, ( * ri)i a n St a n dard — Ca n dh • , St a n da rd. ) 

Candle, Concentric. An electric candle of the JablochkofT type, 
having a small solid carbon inside of an outside tubular carbon, the 
space "between being tilled with refractory material corresponding 
to the colombin, q. v., of the ordinary type. The arc springs across 
from one carbon to the other. 

Candle, Debrun. An arc lamp with approximately parallel 
carbons. A transverse priming connects their bases, and the arc 
starting there at once flies out to the end. 

Candle, Decimal. A standard of illuminating power, proposed 
to the Congress of Electricians of 1889 by Picou. It is one- 
twentieth of a Viole, or almost exactly one standard candle. (See 
/ 'iolcs Standard 0/ Illuminating Power. ) 

Candle, Electric. An arc lamp regulated by simple gravity, or 
without any feed of the carbons or special feeding apparatus, 
generally for the production of an arc light of low intensity. This 
definition may be considered too clastic, and the word may be 
restricted to parallel carbon lamps in which the arc springs across 
from carbon to carbon. For the latter class an alternating current 
I to keep the carbons of equal length. They arc but little 
used now. Various kinds have been invented, some of which are 
given here. 

Candle, German Standard. A standard of illuminating power 
i w Germany. It is a paraffin candle, 6 to the pound, 20 

millimeters diameter ; flame, 56 millimeters high ; rate of con- 
sumption, 7.7 grams per hour. Its value is about two per cent, 
lower than the English standard candle. 

Candle Holder. A clam]) for holding electric candles of the 
hkofftype. The ones shown in the- cut designed forjabloch- 
lir of metallic clamps, each member insu- 
lated from the other, and terminals Of the circuit. 
When the candle is □ the metal pieces press 
St the car' and thus convcv the current. 



IOO 



STANDARD ELECTRICAL DICTIONARY. 



Below each member of the clamps is a binding screw for the Hue 
wire terminals. 




Fitf. jf\ )ABLO< H 



JaBLOCHM 



Candle, Jablochkoff. An arc lamp without regulating mechan- 
ism, producing an arc between the ends of parallel carbons. It 
consists of two parallel rods of carbon, between which is an insulat- 
ing layer of non-combustible material called theCOlotnbtn. Kaolin 
was originally employed for this part ; later, as the fusion of this 
material was found to short-circuit the arc, a mixture of two parts 
of calcium sulphate and one of barium sulphate was used. The 
carbons are 4 millimeters f. 1 6 inch) thick, and the colombin is 
3 millimeters (.12 inch) wide and two-thirds as thick. A little 

slip of carbon is placed across the top, touching both carbons b 

start the arc. ( )nce started the candle burns to the end, and can- 
not be restarted after ignition, except by placing a short conductor 
across the ends, as at first. The Jablochkoff candle may now be 
considered as virtually extinct in this country. In Prance at one 
time a great number were in use. 

To keep the carbons of equal length an alternating current 
must always be used with them. Special alternating combina- 
tions were employed in some cases where a direct current had to 
be drawn upon. 

Candle, Jamin. An arc lamp with approximately parallel car- 
bons, one of which oscillates and is controlled by an electro-magnet 
and armature. A coil of wire is carried around the carbons to 
keep the arc steady and in place. The frame and wire coils have 
been found unsatisfactory, as causing a shadow. 

Candle Power. The amount of light giyen by the standard 
candle. The legal English andstandard American candle is a sperm 



STANDARD ELECTRICAL DICTIONARY. 



W 



candle burning two grains a minute. It should have burned sonic 
ten minutes before use, and the wick should be bent over and have 
a red tip. Otherwise its readings or indications arc useless. A 
sixteen candle power lamp means a Lamp giving the Light o( six- 
teen candles. The candle power is a universal unit of illuminating 
power. 

Candle Power,Rated. The candle power of arc lamps is always 

Stated in excess of the truth, and this may be termed as above. A 
2000 candle power Lamp really gives about 800 candles illumina- 
tion. 

Synonym — Nominal Candle Power. 

Candle Power, Spherical. The average candle power of a source 
of light in all directions. An arc 
lamp and an incandescent lamp vary 
greatly in the intensity of light 
emitted by them in different direc- 
tions. The average of a number of 
determinations at various angles, 
the lamp being moved about into 
different positions, is taken for the 
spherical candle power. 

Candle, Standard. A standard 
of illuminating power. Unless 
otherwise expressed the English 
standard sperm candle is indicated ff m 
by this term. (See Candle Power.) 

Candle, Wilde. An arc lamp with 
approximately parallel carbons. One 

of the carbons can rotate through a Fig- 73. Wilde Candle. 

small arc being pivoted at its base. This oscillation is regulated 
by an electro- magnet at its base, and the carbons touch when no 
current is passing. They separate a little when the current passes, 
establishing an arc. The regulation is comparable to that of a 
regular arc lamp. 

Caoutchouc. India rubber; a substance existing in an emul- 
sion or solution in the juice of certain trees and vines of the tropics, 
whence it is obtained by coagulation and drying. The name 
"rubber" is due to the fact that one of its earliest uses was for 

g pencil marks by rubbing. It has a very high vahu 
insulator. The 1111 worked crude rubber is called virgin gum ; alter 
working over by kneading, it is termed masticated or pure gum 
rubber; after mixture with sulphur and heating, it is termed vul- 
canized rubber. If enough sulphur is added it becomes hard, and if 




102 vSTANDARD ELECTRICAL DICTIONARY. 

black, is termed ebonite ; if vermilion or other pigment is also added 
to produce a reddish color, it is termed vulcanite. The masticated 
gum dissolves more or less completely in naphtha (sp. gr., .850) 
benzole, turpentine, chloroform, ether and oilier similar Liquids. 
The resistance per centimeter cube of "Hooper's" vulcanized 
India rubber, such as is used in submarine cables is 15,000 X io ,,J 
ohms. The specific inductive capacity of pore India rubber is 2.34 
— of vulcanized 2.94 (Schiller). 

Synonyms — India Rubber — Rubber. 

Capacity, Dielectric. The capacity of a dielectric in retaining 

an electrostatic charge; the same o& Specific Inductive Capacity, 
The number expressing it is sometimes called the dielectric con- 
stant. (See Capacity , Specific Inductive.} 

Capacity, Electric, or Electrostatic. The relative capacity of 
a conductor or system to retain a charge of electricity with the pro- 
duction of a given difference of potential, 'flu- greater the cha 
for a given change of potential, or the Less the change of potential 
for a given charge the greater the capacity. The measure of its 
capacity is the- amount of electricity required to raise the- potential 

to a stated amount. The unit of capacity IS the farad, q. v. 1 

trie capacity is comparable- to the capacity of a bottle for air. A 

given amount of air will rai^c the pressure more or less, and the 

amount required to raise its pressure a stated amount might be 

taken as the measure of capacity, and would be Strictly Comparable 

to electrostatic charge and potential change. The capacity, K, is 
obviously proportional to the quantity, Q, of the charge at a given 
potential, K, and inversely proportional to the- potential, B, for a 
given quantity, Q, 

Or, 1 1 I K (_) K and 2 Q K B, 

or, the quantity required to raise a conductor by a given potential 
is equal to the capacity of the conductor or system multiplied by 

the rise of potential. The capacity of a conductor depends upon 

its environments, such as the nature of the dielectric surrounding 
it, the proximity of oppositely charged bodies and other similar 

factors. (vScc Dielectric — ( ondenser — Leyden Jar. 1 

The dimensions of capacity are found by dividing a quantity of 

electricity by the potential produced in the conductor by such 
quantity. 

Quantity (M*l/) ~ potentia (M-L ? T J ) T 2 b. 

Capacity, Instantaneous. The capacity of a condenser when 
connected only for an instant to a source of electricity. This is in 
contrast to electric absorption (see Absorption, Electric)^ and is 
capacity without such absorption taking part in the action. 



STANDARD KU-CTRICAI, DICTIONARY. 103 

Capacity of a Telegraph Conductor. The electric capacity of 
a telegraphic conductor is identical in quality with that of any 
other conducter. It varies in quantity, not only for different wires, 
but tor the same wire under different environments, as the wire 
reacting through the surrounding air or other dielectric upon the 
earth, represents one element of a condenser, the earth, in general, 
representing the other. Hence, a wire placed near the earth has 
greater capacity than one strung upon high poles, although the 
wires may be identical in length, material and diameter. The effect 
of high capacity is to retard the transmission of intermitting 
signals. Thus, when— as in the Morse system- a key is depressed, 
closing a long telegraph current and sending a signal into a line, 
it is at least very probable that a portion of the electricity travels 
to the end of the wire with the velocity of light. But as the wire 
has to be charged, enough current to move the relay may not reach 
the end for some seconds. 

Capacity of Polarization of a Voltaic Cell. The relative 
resistance to polarization of a voltaic cell, measured by the quantity 
of electricity it can supply before polarization. A counter-electro- 
motive force may be developed, or the acid or other solution may 
become exhausted. The quantity of electricity delivered before 
this happens depends on the size and type of cell and other 
factors. 

Capacity, Residual. When two insulated conductors are separ- 
ated by a dielectric, and are discharged disruptively by being con- 
nected" or nearly connected electrically, on removing the discharger 
it is found that a slight charge is present after a short interval. 
This is the residual charge. 'See Charge, Residual.) Shaking or 
jarring the dielectric facilitates the complete discharge. This 
retaining of a charge is a phenomenon of the dielectric, and as 
such, is termed residual capacity. It varies greatly in different 
substances. In quartz it is one-ninth what it is in air. Iceland 
spar (crystalline calcitei seems to have no residual capacity* The 
action of shaking and jarring in facilitating a discharge indicates a 
mechanical stress into which the electrostatic polarization of the 
conductor has thrown the intervening dielectric. 

Capacity, Specific Inductive. The ratio of the capacity of 
a condenser when its plates are separated by any substance to 
the capacity of the same condenser when its plates are separated 

by air. 

A static accumulator consists of two conducting surfaces separated 
by an insulator. It is found that the capacity of an accumulator 

for an electric charge, which varies with or may be rated by the 
potential difference to which its conductors will be brought by the 



io4 



STANDARD ELECTRICAL DICTIONARY. 



given charge, varies with the nature of the interposed dielectric, 
and is proportional to a constant special to each substance. This 
constant is the specific inductive capacity of the dielectric. 

The same condenser will have a higher capacity as the dielectric 
is thinner, other things being equal. But different dielectrics 
having different specific inductive capacities, the constant may be 
determined by ascertaining the relative thicknesses of layers having 
the same total inductive capacity. The thicker the layer, the 
higher is its specific inductive capacity. 

Thus it is found tli.it 3.2 units thickness of sulphur have the 
same total inductive capacity as I unit thickness of air. In other 
words, if sulphur is interposed between two conducting plates, they 
may be separated to over three times the distance that would be 

requisite to retain the same capacity in air. Hence, sulphur is 
the better dielectric, and air being taken as unity, the Specific 
inductive capacity of sulphur is 3.2. 

The specific inductive capacity of a dielectric varies with the 
time and temperature. That of glass rises 2% per cent, between 
12° C. (53. 6° P.) and 83 C. (181.4 b. • If a condenser is dis- 
charged disruptively, it retains a small residual charge which it 
can part with Later. If a metallic connection is made between the 
plates, the discharge is not instantaneous. Vibration shaking and 
jarring facilitate the complete discharge. All this shows that the 

charge is a phase of the dielectric itself, and indicates a strained 

state into which it is brought. 

The following table gives the specific inductive capacity of various 
substances : 

Specific Inductive ( \ipacity. 



Substance. 



Inductive 
Capacity. 



Vacuum, air at about 0.001 milli- 
meter pressure 

Vacuum, air at about 5 millimeters 
pressure 

Hydrogen at about 760 millimeters 
pressure .... 

Air at about 760 millimeters 
pressure .... 

Carbonic Dioxide at about 760 
millimeters pressure 

Olefiant Gas at about 760 millime- 
ters pressure .... 

Sulphur Dioxide at about 760 milli- 
meters pressure 



0.94 about 

f o. 9 o\s 
I 0.99941 
1 0.9997 
I 0.999S 

I 

i 1.000356 

I 1.000S 

1.000722 



u< 



537 



Authority. 



Ayrton. 

Ayrton. 

Holt/maim. 

Boltzmann. 

Ayrton. 
Taken as the 

standard. 
Bolt/.mann. 
Ayrton. 

Boltzmann. 
Avrton. 



STANDARD ELECTRICAL DICTIONARY. 



1 05 



Specific Induct ii't 


' Capacity. — Continued. 


Substance. 


Specific Inductive 
Capacity. 


Authority, 






fl.92 

I.96 




Schiller. 
Wullncr. 


in Wax, Clear 




-1 1-977 
[2.32 




Gibson and 

Barclay. 
Boltzmann. 


Paraffin Wax, Milky 




2.47 




Schiller. 


India Rubber, Pure . 




2-34 




Schiller. 


Vulcanised . 




2.94 




Schiller. 


Resin .... 




2-55 
(2.56 




Boltzmann. 

Wiill ner. 


Ebonite .... 




^2.76 




Schiller. 


Sulphur .... 




(3-i5 

f 2.S8 to 3. 

13-84 


21 


Boltzmann. 
Wiill ner. 
Boltzmann, 


Shellac .... 




2.95 to 3. 


73 


Wiillner. 


Guttapercha 

Mica .... 




4.2 
5 






Flint Glass, Very light . 

" Light . 
Dense . 




6.57 
6.85 
7-4 




1 

j-J. Hopkinson. 


Double extra del 


lse 


10. 1 




J 



Capacity, Unit of. The unit of capacity is the capacity of a sur- 
face which a unit quantity will raise to a unit potential. The 
practical unit is the surface which a coulomb will raise to one volt, 
and is called the farad, q. v. 

Capacity, Storage. In secondary batteries the quantity of 
electrical current which they can supply when charged, without 
undue exhaustion. It is expressed in ampere-hours. The poten- 
tial varies so little during the discharge that it is assumed to be 
constant. 

Capillarity. The reaction between liquid surfaces of different 
kinds or between liquid and solid surfaces due to surface tension. 
Its phenomena are greatly modified by electric charging, which 
;he surface tension. Capillarity is the cause- of solutions 
"crec: nned. Thus in gravity batteries a crust of zinc 

sulphal over the edge of thejar due to the solution creep- 

Liquid withdraws from a surface which it 
prevented by coating the edge 
with paraffin wax, something which water does not moisten. It 



106 STANDARD ELECTRICAL DICTIONARY. 

also causes the liquids of a battery cell to reach the connections and 
injure them by oxidation. The solutions creep up in the pores of 
the carbons of a battery and oxidize the clamps. To give good 
connections a disc of platinum or of lead is used for the contact 
as not being attacked. Another way is to dip the upper ends of 
the dry and warm carbons into melted paraffin wax, or to apply 
the wax to the hot carbons at the top, and melt it in with a hot 
iron. 

Carbon, (a) One of the elements; atomic weight, 12. It exists in 
three allotropic modifications, charcoal, graphite and diamond. In 
the graphitic form it is used as an electric current conductor, as in 

batteries and for arc lamp electrodes, and incandescent lamp fila- 
ments. It is the only substance which conducts electricity and 
which cannot be melted with comparative ease bv incre 

current. | Sec Resistance, ) 

(b) The carbon plate of a battery <>r rod of an arc lamp. To 
secure greater conductivity ill lamp carbons, they are sometimes 
plated with nickel or with copper. 

((' I :'. To place carbons in arc Lamps. This has generally to 
be done once in twenty-four hours, unless the period of burning 
is very short. 

Carbon, Artificial. For Lamps, carbons and battery plan 

bpns are made by igniting, while- protected from the action of the 

air, a mixture of carbon dust and a cementing and carbonizable 
substance. Lam]) black may be added also. Powdered d 

gas carbon is mixed with molasses, coal tar, Byrup, or some simi- 
lar carbonaceous Liquid. It IS moulded into shape. For lam]) 
carbons the mixture is forced from a vessel through a round aper- 
ture or die, by heavy pressure, and is cut into suitable Lengths, i ; <>r 
battery plates it may by simply pressed into moulds. The carbons 
are ignited in covered vessels and also covered with charcoal dust, 
lam]) black or its equivalent. They are heated to lull redness 
for some hours. After removal and cooling they are sometimes 
dipped again into the Liquid used for cementing and reignited. 
Great care in securing pure carbon is aometimes necessary, espe- 
cially for lamps. Fine bituminouscoal is sometimes used, originally 
by Robert Buusen, in [838 or 1840 ; purification by different proc- 
esses has since been applied ; carbon from destructive distillation of 
coal tar has been used. The famous Carre* carbons are made, it is said. 
from 15 parts very pure coke dust, five parts calcined lamp-black, 
and seven or eight parts sugar-syrup mixed with a little gum. Five 
hours heating, with subsequent treatment with boiling caramel 
and reignition are applied. The latter treatment is termed 
" nourishing." Napoli used three parts of coke to one of tar. 
Sometimes a core of different carbon than the surrounding tube is 
employed. 



STANDARD ELECTRICAL DICTIONARY. 107 

The following are the resistances of Carre's carbons per meter 
I 39.37 inches') : 

Diameter in Resistance in Ohms. 

Millimeters. Diameter 111 Inches. @ 20 C. (98 F.) 

1 .059 50.000 

2 .078 12.5 
•117 5-55 

4 -156 3-125 

5 - J 95 2 -ooo 

6 .234 1.390 
S .312 .781 

10 .390 .5 

12 .468 .348 

15 .585 .222 

is .702 .154 

20 .7S0 .125 

At high temperatures the resistance is about one-third these 
amounts. A layer of copper may increase the conductivity one 
hundred times and prolong the duration 14 per cent. Thus a layer 
of copper 1-695 millimeter ( 1-17300 inch) thick increases the con- 
ductivity 4 ! 2 times ; a coating 1-60 millimeter (1-1500 inch) thick 
increases the conductivity one hundred and eleven times. 

Carbon, Cored. A carbon for arc lamps with a central core of 
softer carbon than the exterior zone. It fixes the position of the 
are, and is supposed to give a steadier light. 

Synonym — Concentric Carbon. 

Carbon Holders. In arc lamps, the fixed clamps for holding the 
ends of the carbons. 

Carbonization. The igniting in a closed vessel, protected from 
air, of an organic substance so as to expel from it all the constituents 
except part of the carbon ; destructive distillation. (See Carbon- 
ized Cloth.) 

Carbonized Cloth. Cloth cut in discs and heated in vessels 

protected from the air, until reduced to carbon. The heating is 

sometimes conducted in VOCUO, They are placed in a pile in a 

r other insulating tube, and offer a resistance which can be 

varied by pressure. The greater the pressure the less will be the 

nee, and vice versa. 

Carbon Dioxide. A compound gas, C 2 . It is composed of 
Carbon, 12 parts by weight. 

• ygen, 32 u 
Specific gravity, 1.524 Dulong and Berzelins), 

Molecular weight, 44. 



108 STANDARD ELECTRICAL DICTIONARY. 

It is a dielectric of about the resistance of air. Its specific 
inductive capacity at atmospheric pressures is 
1.000356 (Boltzmami . 

1.000S 1 Ayrton . 

Synonyms — Carbonic Acid — Carbonic Acid I 

Carbon, Volatilization of. In arc lamps the heat is so intense 
that it is believed that part of the carbon is volatilized as vapor 
before being burned or oxidized by the oxygen of the- air. The 

same volatilization may take place in incandescent lamps which are 
overheated. 

Carcel. The standard of artificial illumination used in Prance. It 
is the light yielded by a standard Lamp burning 42 gram 
of colza oil per hour, with a name 40 millimeters 1.57 inch' in 
height. One carcel is equal to candles. 

Carcel Lamp. The lamp giving the standard of illuminating 
power. The wick is cylindrical, giving an Argand or central 

draft flame. It is woven with 75 Btrands, and weighs 3.6 grams 55.5 

grains) per decimeter (3.9 inches of length. The chimney is 
centimeters ( 1 1.3 inches high, 17 millimeters r. 88 inch indiami 

at the bottom, contracting just above the- wick to 34 millime; 
inch). 

Carcel Gas Jet. A standard Ajgand gas burner, made with 

proper rating to give the light of a definite number of carcels illu- 
minating power. Cognizance must b- F the quality of the 

gas as well as of the burner used. 

Carrying Capacity. In a current conductor, its capacil 
carrying a current without becoming unduly heated. It i- 
pressed in amperes. Sec Wire Gauge y . Xtnerican, 1 

Cascade. The arrangement of Leyden jars in series on insulating 

supports, as described below. 

Cascade, Charging and Discharging Leyden Jars in. An 
arrangement of Leyden jars in series for the purpose of charging and 
discharging. They arc placed on insulating supports, the inner coat- 
ing of one connected with the outer coating of the next one all through 
the series. The actual charge received by such a series, the outer 
coating of one cud jar being grounded, and the inner coating of the 
other being connected to a source of high potential, or else the 
same being connected to electrodes of opposite potentials is no 
greater than that of a single jar, but a much higher potential differ- 
ence can be developed without risk of perforating the glass of ajar. 
The difference of potential in each jar of the series is equal to the 
total potential difference divided by the number of jars. The 



STANDARD ELECTRICAL DICTIONARY. 109 

energy of discharge is equal to the same fraction of the energy o{ a 
single jar charged with the same quantity. 

Case=hardening:, Electric. The conversion of the surface of 
iron into steel by applying a proper carbonaceous material to it 
while it is heated by an electric current. It is a superficial cementa- 
tion process. 

Cataphoresis. Electric osmore ; the transfer of substances in 
solution through porous membranes under the influence probably 
of electrolysis, but without themselves being decomposed. 

Cautery, Electric. An electro-surgical appliance for removing 
diseased parts, or arresting hemorrhages, taking the place of the knife 
or other cutting instrument. The cautery is a platinum wire heated 
to whiteness by an electric current, and when 111 that condition 
used to cut off tumors, stop the flow of blood and parallel operations. 
The application is painful, but by the use of anaesthetics pain is 
avoided, and the healing after the operation is greatly accelerated. 

The heated wire of the cautery can be used for cutting opera- 
tions in many cases where excision by a knife would be almost 
impracticable. 

Synonyms — Galvano-cautery — Galvano-caustry — Galvano-elec- 
tric, do. — Galvano-thermal, do. 

C. C. A contraction of cubic centimeter. It is often written in 
small letters, as 100 c. c, meaning 100 cubic centimeters. 

Cell, Constant. A cell which yields a constant and uniform 
current under unvarying conditions. This implies that neither 
the electro-motive force or the resistance of the cell shall vary, or 
else that as the electro-motive forces run down the resistance shall 
diminish in proper proportion to maintain a constant current. 
There is really no constant cell. The constancy is greatest when 
the external resistance is high in proportion to the internal 
nee. 

Cell, Electrolytic. A vessel containing the electrolyte, a liquid 
decomposable by the current, and electrodes, arranged for the 
passage of a decomposing current. The voltameter, q. v., is an 
example. 

Cell, Standard Voltaic. A cell designed to be a standard of 
electro-motive force ; one in which the same elements shall always 
be present under the to develop the same 

electro-motive force. In use the circuit is closed only for a very 
short time, so that it shall not become altered by polarization or 

exhaustion. 

Cell, Standard Voltaic, DanielTs. A zinc-copper — copper 
sulphate couple. Many forms are used. Sometimes a number of 



no 



STANDARD ELECTRICAL DICTIONARY. 



pieces of blotting paper arc interposed between two plates, one of 
copper — the other of zinc. The paper next the copper is soaked 
in copper sulphate solution, and those next the zinc in zinc sul- 
phate solution, of course before being put together. Sometimes 
the ordinary porous cup combination is employed. The cut shows 
a modification due to Dr. Fleming [PhiL Mag. S. 5, vol. xx, p. 126), 
which explains itself. The U tube- is ; 4 -inch diameter, and S 
inches long. Starting with it empty the 
tap ./ is opened, and the- whole /'tube 
filled with zinc sulphate solution, and the 
tap A is closed. The zinc rod usually kept 
in the tube L is put in place, tightly* cork- 
ing up its end of the I ' tube. The cock C 

is opened, which lowers the level of the 

solution in the right hand limb of the { ' 
tube only. The tap B is opened and the 

copper sulphate solution is run in, preserv- 
ing the Line <»t separation <>f the- two boIu- 
tions. The copper rod is taken outof its tube 

.!/, and is put in place. India rubber corks 

are used lor both rods. As the Liquids t> 

to mix the mixture can be drawn ofl 

and the- sharp line of demarcation re-estab- 
lished. In Dr. Sloane's standard cell two 

test tubes are employed lor the solutions 
and a Syphon IS US< d to connect them. 

Oxidationof the zinc lowers the £. M. 1 .. 

oxidation of the copper raise-, it. With 

solutionsofequalsp.gr. the- E£. M.F. isi.104 
volts, [f the copper sulphate solution is 

[,IOOSp. gr. and the /111c sulphate solution 
1,400 sp. gr , both at 15 , the K. 

M. K. will be 1.074 volt. Clean pure zinc and freshly electroly/ed 
copper should he used. 

Cell, Standard Voltaic, Latimer Clark's. A mcrcurv and zinc 
electrode couple with mcrcurous sulphate as excitant and depolar- 
izer. The positive element is an amalgam of zinc, the negative 
is pure mercury. Each clement, in a. representative form, the // 
form, is contained in a separate vessel which communicate by a 
tube. Over the pure mercury some mcrcurous sulphate is placed. 
Both vessels are filled to above the level ofthe connecting tube with 
zinc sulphate solution, and kept saturated. It is tightly closed or 
corked. The E. M. F. at I5°C 159" F. 1 is [.438. Temperature cor- 
rection (1 — .00077 (/ — 15 C)) / being expressed in degrees centi- 
grade (Rayleighb A diminution in specific gravity of the zinc 




Fie:. 7Q 

Standard DaNIBLL CsLL 
—Fleming's Form. 



STANDARD ELECTRICAL DICTIONARY. Ill 

solution increases the E. M. F. The cell polarizes rapidly and the 
temperature coefficient is considered too high. 



Fig. 80. Latimer Clark's Standard Cell. 

Cements, Electrical. A few cements find their use in electrical 
work. Marine glue, Chatterton's compound, and sealing wax may 
be cited. 

Centi = . Employed as a prefix to mdicatc one-hundredth, as 
centimeter \ the one-hundredth of a meter ; centi-ampere, the one- 
hundredth of an ampere. 

Centigrade scale. A thermometer scale in use by scientists 
of all countries and in general use in many. The temperature of 
melting ice is o ; the temperature of condensing steam is ioo° ; 
the degrees are all of equal length. To reduce to Eahrenheit degrees 
multiply by 9 and divide by 5. and add 32 algebraically, treating all 
readings below as minus quantities. For its relations to the 
Reamur scale, see Reatnur Scale. Its abbreviation is C, as io° C, 
mean ntigrade. 

Centimeter. A metric system unit of length; one-hundredth 
of a meter; O.3937 inch. The absolute ore. g. s. unit of length. 

Centimeter«£ram=second System. The accepted fundi 

mental or absolul "f units, called the ( '. G* S. system. It 

embraces units of size, weight, time, in mechanics, physics, clec- 



112 STANDARD ELECTRICAL DICTIONARY. 

tricity and other branches. It is also called the absolute system 
of units. It admits of the formation of new units as required by 
increased scope or classification. The following are. basic units of 
the system : 

Of length, centimeter ; of mass, gram ; of time, second : of force, 
dyne; of work or energy, erg. Sec Dyne % Erg. y and other units 
in general. 

Central Station Distribution or Supply. The system of sup- 
plying electric energy in current form from a main generat- 
ing plant to a district of a number of houses, factories, etc. It is 
in contrast with the isolated plant system in which each house or 
factory has its own separate generating installment, lotteries or 
dynamos. 

Centre of Gravity. A point so situated with respect to any 

particular body, that the- resultant of the parallel attracti: 

between the earth and the several molecules of the body 
always passes through it. Tin- HlltantS of the relative 

moments of the molecules, If a body is suspended, as by a string, 
the centre of gravity always lies vertically under its point of sus- 
pension. By two trials the- point of intersection of plumb lines 
from the point of suspension hemg determined the centre of 
gravity is known. The vertical from the poinl of support coin- 
cides with the line of direction. 

Centre of Gyration. The c< ration with respect to the 

axis of a rotating body is a point at which if the entire 1:1 tSS of 
the body were concentrated Us moment of inertia would remain 
unchanged. The distance of this poinl from the axis is the radius 
of gyration. 

Centre of Oscillation. The point referred to in a body, suspended 
or mounted to swing like a pendulum, at which if all the m 
were concentrated, it would complete its oscillations in the same 
time. The distance from the axis of support to this point gj 

the virtual length of the pendulum which the body represent^. 

Centre of Percussion. The point in a suspended body, one 
free to swing like a pendulum, at which an impulse may be 
applied, perpendicular to the plane through the axis of the body 

and through the axis of support without shock to the axis. It 
is identical with the centre of oscillation, q. v., when such lies 
within the body. 

Centrifugal Force. The force which draws a body constrained 
to move in a curved path away from the centre of rotation. It is 
really due to a tangential impulse and by some physicists is called 
the centrifugal component of tangential velocity. It has to be 
provided against in generator and motor armatures, by winding 



STANDARD ELECTRICAL DICTIONARY. 113 

them with wire or bands to prevent the coils of wire from spread- 
ing or leaving their bed upon the core. 

Centrifugal Governor. The usual type of steam-engine governor. 
The motion ot the engine rotates a system of weights, which arc 
forced outward by centrifugal force, "and are drawn inwards by 
gravity or bv springs. Moving outwards they shut off steam, and 
moving inwards they admit it, thus keeping the engine at ap- 
proximated a constant speed. The connections between them and 
the steam supply and the general construction vary widely in 
different governors. 

C. G. S. Abbreviation or symbol for Ccnti)neter-gram-second, 
astheC. G. S. system. [See Centimeter-g ram-second System.) It 
is sometimes expressed in capitals, as above, and sometimes in 
small letters, as the c. g. s. unit of resistance. 

Chamber of Incandescent Lamp. The interior of the bulb of 
an incandescent lamp. ' v See Lamp, Incandescent,) 

Characteristic Curve. A curve indicating the variations in 
electro-motive force developed during the rotations of the armature 
of a dynamo or other generator of E. M. F. The term as used in 



&0 



M 



C-J^aL _i 

o\ ' If 



o 30 



20 30 40 60 CO 
A M PERES. 

Fig. 81. Characteristic Curve of a 
\mo. 




20 30 40 C 30 60 70 



Pic. 82. 
mg Characteristic 



the electrical sense is thus applied, although the indicator diagram 

ae may be term* racteristic curve-, and bo in 

Other Cases j taken from a 1 aerator 

arc increased in number, the E. M. I I may be very rapidly 



114 STANDARD ELECTRICAL DICTIONARY. 

up to a certain point, and thereafter more slowly. To construct 
the curve co-ordinates, q. v., are employed. The resistance of 
the dynamo and of the outer circuit being known, the current 
intensity is measured. To obtain variations in electro-motive 
force the external resistance is changed. Thus a number of ampere 
readings with varying known resistance are obtained, and for each 
one an electro-motive force is calculated by Ohm's law. From 
these data a curve is plotted, usually with volts laid oil on the 
ordinate and amperes on the abscissa. 

By other methods oilier characteristic curves may be obtained, 
for which the titles under Curve may be- consulted. 

Characteristic, Drooping. A characteristic curve of a dynamo 
which indicates a fill in voltage when an excessive current is taken 
from the dynamo in question. It is shown strongly in some Brush 
machines, and is partly due to the arrangements lor cutting out two 
of the coils as they approach the neutral line. It is an savant 
as it protects from overheating on ihort circuit. 

Characteristic, External. In a dynamo the characteristic curve 
in which the relations of volts between terminals to amperes in the 
outer circuit arc plotted. Sec ( ui \ i . E \ t<) nal ( haracteristic, I 

Characteristic, Internal. A characteristic curve of a shunt 

dynamo, in which the relations of vol ts to amperes in the shunt 
circuit is plotted. 

Characteristics of Sound. Of interest, electrically, 
ing the telephone, they compri 
(i) Pitch } due to frequency of vibrations. 

(2) Intensity or loudness, due to amplitude of waves of sound. 

(3) Quality or timbre, the distinguishing characteristic 
any specific sound due to overtones, discords, etc., by which 
the sound is recognizable from others. The telephone is held by 
the U. S. courts to be capable ^t reproducing the voice by means of 
the undulatory current. < See ( urrent, I naulatory. 1 

Charge. The quantity of electricity that is present on the sur- 
face of a body or conductor. If no electricity is supplied, and the 
conductor is connected to the earth, it is quickly discharged. A 
charge is measured by the units of quantity, such as the coulomb. 
The charge that a conductor can retain at a given rise of potential 
gives its capacity, expressible in units of capacity, such as the farad. 
A charge implies the stretching or straining between the surface 
of the charged body, and some complimentary charged surface or 
surfaces, near or far, of large or small area, of even or uneven 
distribution. 

Charge, v. (a) To introduce an electrostatic charge. 
charge a condenser. 



STANDARD ELECTRICAL DICTIONARY. 115 

(6) To decompose the elements of a secondary battery ^ q. v., so as 

to render it capable of producing a current. Thus, a spent battery 
is charged or recharged to enable it to do more work. 
Synonyms — Renovate — Revivify — Recharge. 

Charge, Bound. A charge of electricity borne by the surface of 
a body so situated with reference to another oppositely charged 
body, that the charge is imperceptible to ordinary test, will not 
affect an electroscope nor leave the surface if the latter is connected 
to the earth. To discharge such a body it must be connected to 
Its complimentariiy charged body. The bound charge was for- 
mcrlv called dissimulated or latent electricity. ^See Charge^ 

The charge or portion of a charge of a surface which is neutral- 
ized inductively by a neighboring charge of opposite kind. The 
degree of neutralization or of binding will depend on the distance 
of the two charged surfaces from one another and on the electro- 
static nature of the medium intervening, which must of necessity 
be a dielectric. A charge not so held or neutralized is termed 
a free charge. Thus a surface may be charged and by the 
approach of a surface less highly charged may have part of its 
charge bound. Then if connected to earth, it will part with its 
unbound or free charge, but will retain the other until the bind- 
ing surface is removed, or until the electricity of such surface is 
itself bound, or discharged, or until connection is made between 
the two surfaces. Thus a body may have both a bound and a free 
charge at the same time. 

Charge, Density of. The relative quantity of electricity upon 

a given surface. Thus a charged surface may have an evenly dis- 
tributed charge or one of even density, or an unevenly distriouted 
charge or one of uneven density. In a thunderstorm the earth 
denser charge under the clouds than elsewhere. 
Synonym — Klcctrical Density. 

Charge, Dissipation of. As every body known conducts elec- 
tricity, it is impossible so to insulate a surface that it will not lose 
its charge by leakage. An absolute vacuum might answer, and 
Crookcs in a high vacuum has retained a charge against dissipa- 
tion for years. The gradual loss is termed as above. 

Charge, Distribution of. The relation of densities of charge 
on different pari Lbody. On a spherical conductor the 

Charge is normally of c vc :i distribution ; on other conductors it is 

Ibuted, be density at points, edges, 

and] Uest radius of curvature-. Even distribution can 

turbed by local induction, due to the presence of oppo- 
site] 



n6 STANDARD ELECTRICAL DICTIONARY. 

Charge, Free. The charge borne by an insulated body, independ- 
ent of surrounding objects. Theoretically it is an impossibility. A 
charge always has its compliment somewhere in surrounding 
objects. As a matter of convenience and convention, where the com- 
plimentary charge is so distributed that its influence is not per- 
ceptible the charge is called a free charge. If connected to earth 
the free charge will leave the body. If the body is connected with 
an electroscope the free charge will affect the same . (See Charge t 
J,' on nd.) 

Charge, Residual. When a Lcyden jar or other condenser is 

discharged by the ordinary method, after a few minutes standing a 
second discharge of less amount can be obtained from it. This is 
due to what is known .as the residual charge. It seems to be con- 
nected in some way with the mechanical or molecular distortion of 
the dielectric. The jarnng of the dielectric after discharge favors 
the rapidity of the action, diminishing the time required for the 
appearance of the residual charge. The phenomenon, it will Ik 
is analogous to residua] magnetism. This charge is the reciprocal 
of electric absorption and depends J«»r its amount upon the nature 

of the dielectric, i Sec- . \bsorption x EUi tric } and Capacity^ Residual, i 
Synonym — Electric Residue. 

Chatterton's Compound. A cement used for cementing 
together Layers or sheets ofgutta percha, and for similar purposes 
in splicing telegraph cables, tts Formula is : 

Stockholm Tar. i part. 

Resin, i part. 

Gutta Percha, ; part^. 

All parts by weight. 

Chemical Change. When bodies unite in the ratio of their 
chemical equivalents y so as to represent the satisfying of affinity or the 

setting free of thermal or Other energy, which uniting is gcncrallv 
accompanied by sensible heat and often by light, as in the ignition 
of a match, burning of a candle, and, when the new compound 
exhibits new properties distinct from those of its components, a 
chemical combination is indicated. More definitely it is a change 
of relation of the atoms. Another form of chemical change is 
decomposition, the reverse of combination, and requiring or absorb- 
ing energy and producing several bodies of properties distinct 
from those of the original compound. Thus in a voltaic battery 
chemical combination and decomposition take place, with evolu- 
tion of electric instead of thermal energy. 

Chemical Equivalent. The quotient obtained by dividing the 
atomic weight, q. v., of an element by its valency, q. v. Thus the 
atomic weight of oxygen is 16, its valency is 2, its chemical equiv- 
alent is 8. It is the weight of the clement corresponding to a unit 



STANDARD ELECTRICAL DICTIONARY. n; 

weight of hydrogen, cither as replacing it, or combining with it. In 

electro-chemical calculations the chemical equivalent is often con- 
veniently used to avoid the necessity of dividing by the valency 
when atomic weights are used. The latter is really the better 
practice. The atomic weights in the old system of chemical nomen- 
clature were chemical equivalents. 

Chemical Recorder. A form of telegraphic recorder in which 
the characters, often of the Morse alphabet or some similar one, arc 
inscribed on chemically prepared paper by decomposition affecting 
the compound with which the paper is charged. In the original 
chemical recorder of Bain, the instrument was somewhat similar to 
the Morse recorder, except that the motionless stylus, S, always press- 
ing against the paper was incapable of making any mark, but being 
of iron, and the paper strip being impregnated with potassium 
ferrocyanide, on the passage of a current a stain of Prussian blue 
was produced where the stylus touched the paper. The current 
passes from the line by way of the iron stylns, through the paper, 
and by way of a brass surface, J/, against which the paper is held and 
is pressed bv the stylus, to the earth. This recorder is extremely 
simple and has no part to be moved by the current. The solution 
in which the paper is dipped contains a mixture of potassium 
ferrocyanide and ammonium nitrate. The object of the latter is to 
keep the paper moist. In recent recorders a solution of potassium 
iodide has been used, which gives a brown stain of free iodine, when 
the current passes. This stain disappears in a few days. 




Fig. 83. Bain's Telegraph Employing Chemical Recorder. 

In the cut. R is the roll of paper, //is a tank of solution with roll, 

ingthe paper; M is the brass surface against which 

;hc iKi]»rr. PP\ //'. Ware feed rollers; Tla 

itting key, and /'/are earth plates. 

wn duplicated for each end. 



n8 



STANDARD ELECTRICAL DICTIONARY. 



Chemistry. The science treating of atomic and molecular rela- 
tions of the elements and of chemical compounds of the same. 

Chimes, Electric. An apparatus employed to illustrate the 

principles of the electrostatic charge, involving the ringing of bells 
by electrostatic attraction and repulsion. It is used in connection 
with a frictional, or influence electric machine. Two bells are cm- 
ployed with a button or clapper suspended between them. One 
bell is connected to one of the prime conductors, q, v., of the 
machine. The other insulated therefrom is connected to earth, or 
if an influence machine is nsed, to the other prime conductor. The 
clappers are hung by a silk thread, so as to be- entirely insulated. 
On working the machine the bells become- oppositely excited. A 
clapper is attracted to one then when charged i> repelled and 
attracted to the Other, it gives Up its charge and becoming charged 

with similar electricity to that of the bell it touches, is repelled and 
attracted to the other, and this action is kept up as long as the 
excitement continues, the bells ringing continuously. 




V\'j;. 84. Electric Chimes. 

Chronograph, Electric. An apparatus for indicating electric- 
ally, and thereby measuring, the lapse of time. The periods meas- 
ured may be exceedingly short, such as the time a photographic 
shutter takes to close, the time required by a projectile to go a 
certain distance, and similar periods. 

A drum rotated with even and known velocity may be marked 
by a stylus pressed upon it by the action ot an electro-magnet 
when a key is touched, or other disturbance. Then the space 
between two marks would give the period elapsing between the 
two disturbances of the circuit. As it is practically impe^ssiblc to 
secure even rotation of a drum, it is necessary to constantly 
measure its rate of rotation. This is effected by causing a tuning- 



STANDARD ELECTRICAL DICTIONARY. 



119 



fork of known rate oi vibration to be maintained in vibration 
electrically. A line point or bristle attached to one of its arms, 
marks a sinnons line upon the smoked surface of the cylinder. 
This gives the basis for most accurately determining the smallest 
intervals. Each wave drawn by the fork corresponds to a known 
fraction of a second. 

For projectiles, the cutting of a wire opens a circuit, and the 
opening is recorded instead of the closing. By firing so as to cut 
two wires at a known distance apart the rate is obtained bv the 
chronograph. 

Synonym — Chronoscope. 

Chutaux's Solution. A solution for bichromate batteries. It 
is composed as follows : 

Water, 1,500 parts — Potassium bichromate, 100 parts — mercury 
bisulphate, 100 parts — 66° sulphuric acid, 200 parts. 



Circle, Galvanic or Voltaic. 

obsolete. 



A term for the voltaic circuit ; 




Fig. 85. Magic Circle. 

Circle, Ma^ic. A. form of electro-magnet It i> a thick circle 
of round iron and ia used in connection with a magnetizing coil, 
wn, to illustrate electro-magnetic attraction. 



120 STANDARD ELECTRICAL DICTIONARY. 

Circuit. A conducting path for electric currents properly form- 
ing a complete path with ends joined and including generally a 

generating device of some kind. Part of the conduction may be 
true and part electrolytic. (See Electrolytic Conduction. | The term 
has become extended, so that the term is often applied to any por- 
tian of a circuit conveniently considered by itself. The simplest 
example of a complete circuit would be a circular conductor. If 
rotated in the earth's field so as to cut its lines of force a current 
would go through it, and it would be an electric circuit. Another 
example is a galvanic battery with its ends connected by a wire. 
Here the battery generates the current which, by electrolytic 
conduction, goes through the battery and by true conduction 
through the wire. For an example of a portion of a circuit spoken 
of as " a circuit " sec Circuit, .Astatic. 

Circuit, Astatic. A circuit so wound with reference to the 
direction of the currents passing through it that the terrestrial or 
other lines of force have no directive effect upon it. one member 
counteracting the other. It may bo produced by making the wire 
lie in two closed curves, B and C \ each enclosing an equal area, 
one of identical shape and disposition with the Other, and with the 
current circulating in opposite directions in each one. Tim 
circuit represents a magnetizing turn of opposite polarity and 
counteracting each other's directive tendency exhibited in a field 
of force with reference to an axis a c. 



*--£n 





Figs. 86 and 87. Astatic Circuits. 

Another form oi astatic circuit is shown in Fig. 86. The 

portions B, C, lying on opposite sides of the axis of rotation a c % 



STANDARD ELECTRICAL DICTIONARY. 



arc Oppositely acted on by the earth's directive force as regards the 
dire, their rotation. 

Circuit, Branch. A circuit dividing into two or more parts in 
parallel with each other. 

Circuit Breaker. Any apparatus for opening and closing a 

circuit is thus termed, but it is generally applied to automatic 
apparatus. A typical circuit breaker is the hammer and anvil of the 
induction coil, i See Induction Coil; Anvil A Again a pendulum 
connected to one terminal of a circuit may swing so as to carry a 
point on its lower end through a globule of mercury as it swings, 
which globule is connected to the other terminal. A great many 
arrangements of this character have been devised. 
:. — Contact Breaker. 

Circuit Breaker, Automatic. A circuit breaker worked by the 
apparatus to which it is attached, or otherwise automatically. (See 
:io?i Coil; Anvil; Bell x Elect* 

Circuit Breaker, File. A coarsely cut file, forms one terminal 
of an electric circuit, with a straight piece of copper or steel for the 
other terminal. The latter terminal drawn along the teeth makes 
and breaks the contact once for every tooth. The movable piece 
should have an insulated handle. 

Circuit Breaker, Mercury. A circuit breaker which may be 
identical in principle, with the automatic circuit 
breaker of an induction coil, but in which in 
place of the anvil, q. v., a mercury cup is used, 
into which the end of a wire dips and emerges as 
it is actuated by the impulses of the current. 
Each dip makes the contact, which is broken as 
the wire springs back. The mercury should be 
covered with alcohol to protect it from oxidation. 

Circuit Breaker, Pendulum. A circuit 

breaker in which a pendulum in its swing 
makes and breaks a contact. It may be kept 
in motion by clockwork, or by an electro-mag- 
net, attracting intermittently an armature at- 
tached to its rod, the magnet circuit being 
opened and closed by the pendulum or circuit 
breaker itself. A mercury contact may be used 
with it. 

Circuit Breaker, Tuning Fork. A circuit 
breaker in which atonic j Ices and bn 

the circuit. Each vil one of the 

p 

Thcadj- 




122 



STANDARD ELECTRICAL DICTIONARY. 



ment is necessarily delicate, owing to the limited amplitude of the 
motion of the fork. The fork is kept in vibration sometimes by 
an electro-magnet, which is excited as the circuit is closed by the 
fork. One leg of the fork acts as the armature of the magnet, 
and is attracted according to its own natural period. 

Circuit Breaker, Wheel. A toothed wheel with a spring bear- 
ing against its teeth. One terminal of a circuit connects with the 
wheel through its axle, the other connects with the spring. When 
the wheel is turned the circuit is opened and closed once for each 
tooth. The interstices between teeth on such a wheel may be filled 
with insulating material, giving a cylindrical surface for the con- 
tact spring to rub on. 




Fig. 89 Toothed Wheel Circuit Breaker. 



Circuit, Closed. A circuit whose electric continuity is com- 
plete ; to make an open circuit complete by closing a switch or 
otherwise is to close, complete, or make a circuit. 

Syno?iyms — Completed Circuit — Made Circuit. 

Circuit, Compound. A circuit characterized by compounding 
of generating or receiving devices, as including several separate 
batteries, or several motors, or other receiving devices. It is some- 
times used to indicate a circuit having its battery arranged in series. 
It should be restricted to the first definition. 



STANDARD ELECTRICAL DICTIONARY. 123 

Circuit, Derived. A partial circuit connected to two points of 
another circuit, so as to be in parallel with the portion thereof 
between such two points ; a shunt circuit. 

Synonyms — Shunt Circuit — Derivative Circuit — Parallel Circuit. 

Circuit, Electric, Active. A circuit through which a current 
passes. The circuit itself need only be a conducting ring, or end- 
less wire. Generally it includes, as part of the circuit, a generator 
of electro-motive force, and through which generator by conduction, 
ordinary or electrolytic, the same current goes that passes through 
the rest of the circuit. One and the same current passes through 
all parts of a scries circuit when such current is constant. 

A current being produced by electro-motive force, and electro- 
motive force disappearing in its production in an active circuit, 
there must be some source of energy which will maintain electro- 
motive force against the drain made upon it by the current. 

The simplest conception of an active electric circuit is a ring or 
endless conductor swept through a field of force so as to cut lines 
of force. A simple ring dropped over a magnet pole represents the 
simplification of this process. In such a ring a current, exceed- 
ingly slight, of course, will be produced. In this case there is no 
generator in the circuit. An earth coil (see Coil, Earth,) represents 
such a circuit, with the addition, when experimented with, of a 
galvanometer in the circuit. 

In practice, a circuit includes a generator such as a battery or 
dynamo, and by conductors is led through a continuous path. 
Electric lamps, electrolytic cells, motors and the like may be 
included in it. 

The term 4 ' circuit" is also applied to portions of a true circuit, 
as the internal circuit, or external circuit. A certain amount of 
elasticity is allowed in its use. It by no means necessarily indi- 
cates a complete through circuit. 

Circuit, Electrostatic, (a) A circuit through which an dec- 

:cor high tension discharge takes place. It is virtually an 
electric circuit. 

The term is applied also to the closed paths of electrostatic 
lines of force. 

Circuit, External. The portion of a circuit not included within 
the generator. 

Circuit, Grounded. A circuit, one of whose members, the 
return circuit, is represented by the earth, so that the earth com- 
pletes the circuit. In telegraphy each end of the line i^. grounded 
nnected to an earth-plate, q. v., or to the water or gas-pipes, 
and the current is a>sumed to go through the earth on its return. 



124 



STANDARD ELECTRIC AT, DICTIONARY. 



It really amounts to a discharging at one end, and charging at the 

other end of the line. The resistance of the earth is zero, but the 
resistance of the grounding or connection with the earth may 
considerable. 
Synonyms — Ground Circuit — Earth Circuit -Single Wire Circuit. 

Circuit Indicator. A pocket compass, decomposition appara- 
tus, galvanometer or other device for indicating the condition of a 
wire, whether carrying a current or not, and, if carrying one, 

direction, and sometimes roughly indicating its strength. 

Circuit, Internal. The portion of an electric circuit included 
within the generator. 

Circuit, Line. The portion of a circuil inline 

or conductor, as in a telegraph circuit the line carried on the 

poles; distinguished from the local circuil utt t Local t 
telegraphy. 

Circuit, Local. In telegraphy, a short circuit with local e 

ator or battery included, contained within the limits of the offic 

station and operated by a relay, q, v. This \\ inal local 

circuit ; the term is applicable to any similar arrangement in other 
systems. Referring to the cut. the main line circuit includes the 
main battery, Zs, Key, I\ Relay, A\ ground plates, <>\ G v The 
relay magnet opens and closes the local circuit with its local battery, 
/,, and sounder magnet, I L with its armature, />'. The minor 
parts, such as switches, are omitted. 



\ 



■II II ■ III 




Fig. go. Local Circuit cf Telegraph System. 

Circuit, Local Battery. A local circuit worked by and includ- 
ing a local battery in its course. 



^NDARD ELECTRICAL DICTIONARY. 125 

Circuit, Loop. A minor circuit introduced in scries into an- 
other circuit by a cut-out, or other device, so as to become a 
portion ot the main circuit. 

Circuit Loop Break. A supporter or bracket with two arms 

for carrying insulators. Its use is to enable a loop connection to be 
introduced into a line which is cut. so as to enable the connection 
of the ends of the loop to be made, one to each end of the through 
wire, which ends are attached, one to each of the two insulators. 

Circuit, Alain. The circuit including the main line and appar- 
atus supplied by the main battery, as distinguished from the local 
circuit. (See Circuity Lc 

Circuit, Alain Battery. The main circuit, including the main 
or principal battery in its course. 

Circuit, Metallic. A circuit in which the current outside the • 
generator, or similar parts, is carried on a metallic conductor ; a 
circuit without any ground circuit. The including of a galvanic 
battery or electro plating bath would not prevent the application 
of the term ; its essential meaning is the omission of the earth 
as the return circuit. 

Circuit, Negative Side of. The side of a circuit opposite to the 

positive side. See Circuit ', Positive Side of.) It is defined as the 
half of a circuit leading to the positive terminal of the generator. 

Circuit, Open. A circuit with its continuity broken, as by dis- 
connecting a wire from the battery, or opening a switch ; a broken 
circuit is its synonym. To open a switch or disconnect or cut the 
wire is termed opening or breaking the circuit. 

Synonyms — Incomplete Circuit — Broken Circuit. 

Circuit, Positive Side of. This side is such that an observer 
standing girdled by the current with his head in the positive side 
or region, would see the current pass around him from his right 
toward his left hand. It is also defined as the half of the circuit 
leading to the negative terminal of the generator. 

Circuit, Recoil. The portion of a parallel circuit presenting an 

alternative path, q. v., for a disruptive discharge. 

Circuit, Return, [a) The part of a circuit extending from the 

ic extreme point in general, upon which no apparatus 

'.iced. In telegraph systems the ground generally forms the 

return circuit. The distinction of return and working circuit 

defined a- the portion of a circuit Leading to 

the negative t r 



126 STANDARD ELECTRICAL DICTIONARY. 

Circuits, Forked. Circuits starting in different paths or direc- 
tions from one and the same point. 

Circuit, Simple. A circuit containing a single generator, and a 

single receiver of any kind, such as a motor or sounder, with a single 
connecting conductor. It is also used to indicate arrangement in 
multiple arc, but not generally, or with approval. 

Circuits, Parallel. Two or more conductors starting from a 
common point and ending at another common point are termed 
parallel circuits, although really but parts of circuits. If of equal 
resistance their joint resistance is obtained by dividing the resistance 
of one by the number of parallel circuits. If of unequal resistance 
r, r', r n ', etc., the formula for joint resistance. A', of two is 

R 

r ; ' 
This resistance may then bo combined with a third one by the same 
formula, and thus any number may be- calculated. 
Synonym — Shunt Circuit. 

Circuit, Voltaic. Properly a circuit including a conductor and 

a voltaic couple. 

It is also applied to the electric circuit, q. v., or to any circuit 
considered as a bearer of current electricity. 

Circular Units. Units of area, usually applied t<> cross sectional 

area of conductors, by whose use area is expressed in terms of a 
circle of unit diameter, usually a circular mil, which is the area of 
a circle of one-thousandth of an inch diameter, or a circular milli- 
meter, which is the area of a circle of one millimeter diameter. 
Thus a wire one-quarter of an inch in diameter has an area of 250 
circular mils; a bar one centimeter in diameter has an area of ten 
circular millimeters. 

Circumflux. The product of the total number of conductor 
turns on the armature ofa dynamo or motor, into the current carried 
thereby. For two pole machines it is equal to twice the armature 
ampere-turns ; for four pole machines to four times such quantity 
and so on. 

Clamp. The appliance for grasping and retaining the end of the 
rod that holds a carbon in the arc Lamp. 

Clark's Compound. A cement used for the outside of the sheath 
of telegraph cables. Its formula is : 

Mineral Pitch, 65 parts. 

Silica, 30 parts. 

Tar, 5 parts. 

All parts by weight. 



STANDARD ELECTRICAL DICTIONARY. 127 

Cleats. A support ; a short block of wood, grooved transversely, 
lor holding electric wires against a wall. For the three wire system 
three grooves arc used. The entire wiring of apartments is some- 
times done by the" cleat system,'' using cleats instead, of battens, 
t}. v., or mouldings. The cleats are secured against the wall with 
the grooves facing it, and the wires are introduced therein. 




Fig. 91. Two Wire Cleat. 



J 




Fig. 02. Three Wire Cleat. 



Cleat, Crossing. A cleat with grooves or apertures to support 
wires which cross each other. Two or three grooves are transverse, 
and on the under side, as above ; one groove is longitudinal and on 
the upper side. 

Cleavage, Electrification by. If a mass of mica is rapidly split 
in the dark a slight flash is perceived. Becquerel found that in 
such separation the two pieces came away oppositely charged with 
electricity. The splitting of mica is its cleavage. 

Clock, Controlled. In a system of electric clocks, the clocks 
whose movements arc controlled by the current, regulated by the 
master or controlling clock. 

Synonym — Secondary Clock. 

Clock, Controlling. In a system of electric clocks the master 
clock which controls the movements of the others, by regulating 
the current. 

ftonym—A&astet Clock. 

Clock, Electric Annunciator. A clock operating any form of 
electric annunciator, as dropping shutters, ringing bells", and the 
like, it o] the machinery closing circuits as required at 

any desired hour or inter 



128 STANDARD ELECTRICAL DICTIONARY. 

Clock, Electrolytic. A clock worked by the electrolytic depo- 
sition and resolution of a deposit of metal upon a disc. It is the 

invention of Nikola Tesla. A metallic disc is mounted on a trans- 
verse axis, so as to readily rotate. It is immersed in a vessel <>t 
copper sulphate. A current is passed through the bath, the ter- 
minals or electrodes being near to and facing the opposite edge - 
the disc, so that the line connecting the electrodes lies in the plane 
of the disc. If a current is passed through the solution by the 
electrodes, copper is deposited on one side of the disc, and as it 
rotates under the influence of the weight thus accumulated on one 
vSide, the same metal as it is brought to the other side of thedi- 
redissolved. Thus a continuous rotation is maintained. The cause 

of the deposition and solution is the position of the disc; one-half 

becomes negative and the other positive in their mutual relations. 

Clock, Self=\vindin£ Electric. A clock which is wound peri- 
odically by an c!cctric motor and battery. 

Clockwork, Feed. In arc-lamps the system of feeding the carbon 
or carbons by clockwork whose movements are controlled by the 
resistance of the arc. Thiss; mployedin theSerrin, andin 

the Gramme regulators, among others. The carbons, it* they ap- 
proach, move clockwork. The movement of this 

by an electro-magnet placed in mi. ml atOUnd the arc and carbons. 

Cloisons. Partitions or divisions ; applied t<> the wind 
electro-magnets and coils where the winding is put <>a to the 
full depth, over single sections of the core, one section at a time, 

until the whole core is filled up. 

Closure. The closing or completion of a circuit by depressing a 
key or moving a switch. 

Clutch. In arc lamps a device for the feed of the Upper carbons. 
In its simplest form it is simply a plate or bar pierced with a hole 
through which the carbon passes loosely. The action of the mech- 
anism raises or lowers one end of the plate or bar. As it rises it 
binds and clutches the carbon, and if the action continues it lifts it 
a little. When the same end is lowered the carbon and clutch 
descend together until the opposite end of the clutch being pre- 
vented from further descent, the clutch approaches the horizontal 
position and the rod drops bodily through the aperture. The cut 
shows the clutches of the Brush double carbon lamp. In practice 
the lifting and releasing as regulated by an electro-magnet are so 
very slight that practically an almost absolutely steady feed is 
secured. A similar clutch is used in the Weston lamp. 

Clutch, Electro=magnetic. A clutch or appliance for connect- 
ing a shaft to a source of rotary motion while the latter is in action. 



STANDARD ELECTRICAL DICTIONARY. 



129 



In one form a disc, in whose face a groove has been formed, which 
groove is tilled with a coil of wire, is attracted, to the loose wheel, 
while the shaft carries a flat plate to act as armature. On turning 
on the current the flat plate is attached, adheres, and causes its 




Fig. 93. Clutch of Brush Lamp. 

wheel to partake of the motion of the shaft. Contact is made by 
brushes and collecting rings. 

In the cut, A A is the attracted disc ; the brushes, B B } take cur- 
rent to the collecting rings, C. The magnetizing coil is embedded 
in the body of the pulley, as shown. 




. Kl.F.CTRO-MAGNETIC CLUTCH. 

Coatings of a Condenser or Prime Conductor. The thin con- 
ducting coatings of tinfoil, gold leaf or other conducting substance, 
enabling the surface to receive and part with tin- electric charge 

Without BH< ' ing the charge and discharge would 



i 3 o STANDARD ELECTRICAL DICTIONARY. 

be very slow, and would operate by degrees only, as one part of a 
non-conducting surface might be densely charged and another part 
be quite devoid of sensible charge. 

Code, Cipher. A code of arbitrary words to designate prear- 
ranged or predetermined words, figures or sentences. The systems 
used in commerce have single words to represent whole sentences 
or a number of words of a sentence. This not only imparts a 
degree of secrecy, but makes the messages much shorter. Codes 
are used a great deal in cable transmission. 

Code, Telegraphic. A telegraphic alphabet See Alphabets^ 

Telegraphic. ) 

Coefficient. In algebra, the numerical multiplier of a symbol, 

as in the expression "5 -' '," 5 is the coefficient. In physics, gen- 
erally a number expressing the ratio or relation between quantities, 

one of which is often unity, as a standard or base of the 

coefficients. Thus the coefficient of expansion by heat <>f any 
substance is obtained by dividing its volume for a given degree of 

temperature by its volume at the standard temperature as o C. ox 

32 F. This gives a fraction by which if any volume of a substance, 

taken ato° C, or at whatever may be taken as the basic tempera- 
ture, is multiplied, the expanded volume for the given chao 
temperature will be obtained as the product. A coefficient always 

in some form implies the- idea of a multiplier. Thus the coefficient 

of an inch referred to a foot would be 1-12 or .0833 , because any 
number of inches multiplied by that fraction would give the eor- 
responding number of feet. 

Coefficient, Economic. In machinery, electric generators, 
prime motors and similar structures, the number expressing the 

ratio between energy absorbed by the device, and useful, not neces- 
sarily available, work obtained from it. It is equal to work 
obtained divided by energy absorbed, and is necessarily a fraction. 
If it exceeded unity the doctrine o( the conservation of energy 
would not be true. The economic coefficient expresses the elti- 
cieucy, q. v., of any machine, and of efficiencies there are several 
kinds, to express any one of which the economic coefficient may 
be used. Thus, let W energy absorbed, and w work produced ; 
then wfW is the economic coefficient, and for each case would be 
expressed numerically. (See Efficiency, Commercial — Efficiency, 
Electrical — Efficiency of Conversion . ) 

The distinction between useful and available work in a motor 
is as follows : The useful work would include the work expended 
by the field, and the work taken from the armature by the belt or 
other mechanical connection. Only the latter would be the avail- 
able work. 



STANDARD ELECTRICAL DICTIONARY. 



m 



Coercive or Coercitive Force. The property of steel or hard 
iron, in virtue of which it slowly takes up or parts with magnetic 
force, is thus termed ( M traditionally M ; Daniel!) . It seems to have 
to do with the positions of the molecules, as jarring a bar of steel 
facilitates its magnetization or accelerates its parting, when not in 
a magnetic field, with its permanent or residual magnetism. For 
this reason a permanent magnet should never be jarred, and per- 
mitting the armature to be suddenly 
attracted and to strike against it with 
a jar injures its at- 
tracting power. 

Coercive force is 
defined also as the 
amount of negative 
magnetizing force 
required to reduce 
remanent magnet- 
ism to zero. 

By some authorities the term is 
entirely rejected, as the phenome- 
non does not seem directly a mani- 
festation of force. 

Coil and Coil Plunger. A device 
resembling the coil and plunge, 
q. v., except that for the plunger 
of iron there is substituted a coil 
of wire of such diameter as to 
enter the axial aperture of the 
other, and w r ound or excited in the 
same or in the op- 
posite sense, ac- 
cording to whether 
attraction or repul- 
sion is desired. 

Coil and Plung= 

er. A coil provided 
with a core which 
is free to enter or 
leave the central 
aperture. When 
the coil is excited, 






F:g: .5. Con. and Coil 
Plunger of Mrnoirs Arc 

Lamti 



peri:-!. 



132 



vSTANDARD ELECTRICAL DICTIONARY. 



the core is drawn into it. Various forms of this device have been 
used in arc lamp regulators. 
Synonym — Sucking coil. 

Coil and Plunger, Differential. An 

arrangement of coil and plunger in which 
two plungers or one plunger are acted on 
by two coils, wound so as to act oppositely 
or differentially on the plunger or plun- 
gers. Thus one coil maybe in parallel with 
the Other, and the action on the plunger 
will then depend on the relative cur- 
rents passing through the coils. 

Coil, Choking, A coil of high self- 
induction, used to roist the intensity of 
0T "choke" alternating currents. Any 
COD of insulated wire wound around upon 
B Laminated or divided iron core forms a 
choking coil. The iron coil is usually 
so shaped B8 to afford a closed magnetic 
circuit 

A converter or transformer 
choking coil as long as its secondary is 
Left Open. In alternating current work 

special choking coils are used. Thus for 

theatrical work, a choking coil with a 
movable iron core is used to change the 
intensity of the lights. It is in circuit with the lain]) leads. By 
thrusting in the core the self-induction is increased and the current 
diminishes, lowering the lamps ; by withdrawing it the self-induc- 




Fig. 97. Differential Coil 
AM) PlUNI 




Fig. 9S. Bisected Coils. 

tion diminishes, and the current increases. Thus the lamps can he 
made to gradually vary in illuminating power like gas lights, when 
turned up or down. 

Synonyms — Kicking Coil — Reaction Coil. 

Coils, Bisected. Resistance coils with connections at their 
centers, as shown in the diagram. They are used for comparing the 



STANDARD ELECTRICAL DICTIONARY. 



IA3 



resistances of two conductors. The connections are arranged as 
shown in the coil, each coil being bisected. For the wires, movable 
knife-edge contacts arc employed. The principle of the Wheat- 
stone bridge is used in the method and calculations. 

Coil, Earth. A coil of wire mounted with commutator to be 
rotated so as to cut the lines of force of the earth's magnetic field, 
thereby generating potential difference. The axis of rotation may 
be horizontal, when the potential will be due to the vertical com- 
ponent of the earth's field, or the axis may be vertical, when 
the potential will be due to the horizontal component, or it may be 
set at an intermediate angle. 

Synonym — Delezenne's Circle. 




Fig. 09. Delezenne's Circle or Earth Coil. 

Coil, Electric. A coil of wire used to establish a magnetic field by 
passing a current through it. The wire is cither insulated, or so 
spaced that its convolutions do not touch. 

Coil, Flat. A coil whose windings all lie in one plane, making a 
sort of disc, or an incomplete or perforated disc. 

Coil, Induction. A coil in which by mutual induction the electro- 
motive force of a portion of a circuit is made to produce higher 
or lower electro-motive force in an adjoining circuit, or in a cir- 
cuit, part of which adjoins the original circuit, 01 adjoins part of it. 

An induction coil comprises three principal parts, the core, the 
primary coil and the- secondary coil. If it is to be operated by a 
means must be provided for varying it or opening 
and Closing the primary circuit. A typical coil will be described. 



i 3 4 vSTANDARD ELECTRICAL DICTIONARY. 

The core is a mass of soft iron preferably divided to prevent 
extensive Foucault currents. A cylindrical bundle of soft iron wires 
is generally used. Upon this the primary coil of reasonably heavy 
wire, andof one or two layers in depth, is wrapped, all being carefully 
insulated w T ith shellac and paper where necessary. The secondary 
coil is wrapped upon or over the primary. It consists of very fine 
wire; No. 30 to 36 is about the ordinary range. A great many turns 
of this are made. In general terms the electro-motive force devel- 
oped by the secondary stands to that of the primary terminals in 
the ratio of the windings. This is only approximate. 

The greatest care is required in the insulating. The secondary- 
is sometimes wound in sections so as to keep those parts differing 
greatly in potential far from each other. This prevents sparking, 
which would destroy the insulation. 

A make and break, often of the hammer and anvil type, is oper- 
ated by the coil. (See ( trcuit Breaker^ t lutomatic. | As the cur- 
rent passes through the primary it magnetizes the core. This 
attracts a little hammer which normally resting 011 an anvil com- 
pletes the circuit. The hammer as attracted is lifted from the anvil 
and breaks the circuit. The soft iron core at < nice parts with its 
magnetism and the hammer falls upon the anvil again completing 
the circuit. This operation goes on rapidly, the circuit being 
opened and closed in quick succession. 

Every closing of the primary circuit tends to produce a reverse 
current in the secondary, and every Opening ofthe primary circuit 
tends to produce a direct current in the secondary. Both an 
extremely short duration, and the potential difference of the two 
terminals of the secondary may be very high if there are many 
times more turns in the secondary than in the primary. 

The extra currents interfere with the action of an induction coil. 
To avoid their interference a condenser is used. This consists of 
two scries of sheets of tin foil, heaves of paper alternate with the 
sheets of tin-foil, the whole being built up into a little book. Kach 
sheet of tin-foil connects electrically with the sheet next but one to 
it. Thus each leaf of a set is in connection with all euhcrs of the 
same set, but is insulateel from the others. One set of leaves of 
tin-foil connects with the hammer, the other with the anvil. In 
large coils there may be 75 square feet of tin-foil in the condenser. 

The action ofthe condenser is to dispose of the direct extra cur- 
rent. When the primary circuit is opened this current passes into 
the condenser, which at once discharges itself in the other direction 
through the coil. This demagnetizes the core, and the actiem 
intensifies and shortens the induccel current. The condenser pre- 
vents sparking, and in general improves the action of the coil. 

Many details enter into the constructiem o{ coils, and many 



STANDARD ELECTRICAL DICTIONARY. 135 

variations in their construction obtain. Thus a mercury cup into 
which a plunger dips often replaces the anvil and hammer. 

The induction coil produces a rapid succession of sparks, which 
mav spring across an interval of forty inches. The secondary 
generallv ends in special terminals or electrodes between which the 
sparking takes place. A plate of glass, two inches in thickness, 








Fig. 100. Vertical Section of Induction Coil. 









jr. j 


t 1 


A 


t , - 


H 






6 









Fig. 101. Plan of Induct: \f.ctions. 
can be pierced by them. In the great Si le coil there are 

280 miles of wire in the secondary, and the wire IS about No. \6 

A. \V. (V. 



136 



vSTANDARD ELECTRICAL DICTIONARY. 



Induction coils have quite extended use in electrical work. They 
are used in telephone transmitters, their primary being in circuit 
with the microphone, and their secondary with the line and receiv- 
ing telephone. In electric welding, and in the alternating current 
system they have extended application. In all these cases they 
have no automatic circuit breaker, the actuating current being of 
intermittent or alternating type. 

In the cuts the general construction of an induction coil is shown. 
In the sectional elevation, Fig. kxj, .7, is the iron core ; I> is the 
primary of coarse wire; C is a separating tube, which may be of 
pasteboard ; J) is the secondary of fine wire ; /:, /: arc the binding 
posts connected to the secondary; //, // arc the heads or stand- 
ards ; A', A' are the terminals of the primary ; F is the vibrating 
contact spring ; G t a standard carrying the contact screw ; J is the 
condenser with wires, L, J/, leading to it. 

Referring to the plan, Pig. IO I, //represents the primary coil ; 
B and A are two of the- separate sheets of the condenser, each 
sheet with projecting cars ; ( /, (, are the heads of the coil ; the dark 
lines are connections to the condenser. One set of sheets conn 
with the primary coil at (\ and also with the vibrating spring 
shown in plan and in the elevation at I\ The other set of sheets 
connects with the post, carrying the contact screw. The other 

terminal of the primary runs to a bind- 
ing post /'. I\ in the plan is a binding 
post in connection with the standard 
and contact screw. 

Coil, Induction, Inverted. An 

induction coil arranged to have a lower 
electro-motive force in the secondary 
than in the primary. This is effected 
by having more convolutions in the 
primary wire than in the secondary. 
Such coils in practice arc used with 
the alternating current and then do not 
include a circuit breaker or condenser. 
They arc employed in alternating cur- 
rent system and in electric welding. 
( See U 'elding, Electric — C on i rrler. ) 

In the cut an inverted coil, as con- 
structed for electric welding is shown. 
In it the primary coil is marked P; 
Fig. 102. Inverted Induction th seC ondarv, merely a bar of metal, 
Coil for Electric Welding. . . , / .- ' . . . J . . . . ■ 

is marked zs, with terminals 0,0; the 

heavv coils, /, of iron wire are the core ; A' is a screw for regu- 
lating the clamps ; /, Z is a second one for the the same purpose, 




STANDARD ELECTRICAL DICTIONARY. 137 

while between D and / } ' the heat is produced for welding the 
bars, 7>\ 1>\ held in the clamps. ( ', c '. It will be seen how great 
mav be the difference in turns between the single circle of heavy 
copper rod or bar which is the secondary of the coil, and the long 
coil of wire forming the primary. 

Coil, Induction, Telephone. An induction coil used in tele- 
phone circuits. It is placed in the box or case near the transmitter. 
The primary is in circuit with the microphone. The secondary is in 
circuit with the line and receiving telephone. In the Bell telephone 
apparatus the primary of the induction coil is wound with No. 18 
to 24 A. YV. G. wire to a resistance of y 2 ohm; the secondary, 
with No. 36 wire to a resistance of 80 ohms. The Edison tele- 
phone induction coil was wound with similar wires to a resistance 
of 3 to 4 ohms and of 250 ohms respectively. 

Coil, Magnetizing. A coil of insulated wire for making mag- 
nets ; and for experimental uses ;. it has a short axis and central 
aperture of as small size as consistent with the diameter of the bar 
to be magnetized, which has to pass through it readily. The wire 




Fig. 103. Magnetizing Coil. 

may be quite heavy, 2 or 3 millimeters (.08 — .12 inch) thick, and is 
cemented together with carpenter's glue, or with shellac or ethereal 
solution of gum copal. In use it is passed over the bar a few times 
while a heavy current is going through it. It is used for magic 
circles also. (See Circle, mag 

Coil, Resistance. A coil constructed for the purpose of offering 
a certain resistance to a steady current. This resistance may be 
for the purpose of carrying out quantitative tests, as in Wheatstouc 
bridge work (9ee /, s Bridge) % or simply to reduce the 

intensity of a current. For the first class of work the coils are 
L SO as to prevent the creation of a magnetic field. This is 
doubling the wire without breaking it, and then 
starting at the bend the doubled wire, which is insulated, is wound 

on a bobbin or otherwise until a proper resistance is shown by actual 
■:t. The< generally contained or set in closed 

Blocks <>f bra^s are placed on the- top, 
and one end from one coil and one end from the next connect 



138 STANDARD ELECTRICAL DICTIONARY. 

with the same block. By inserting a plug, P t so as to connect any 
two blocks, which have grooves reamed out for the purpose, the coil 
beneath will be short circuited. German silver, platinoid or other 
alloy, q. v., is generally the material of the wire. A great object is 
to have a wire whose resistance will be unaffected by heat. 





Fig. 104. Rpsistance Coils and Connections, Showing T 

Coil, Rhumkorff. The ordinary induction coil with circuit 
breaker, for use with original direct and constant current, is thus 
termed. ( v Scc Coil, Induction. \ 

Synonym — Endnctorinm. 

Coil, Ribbon. A coil made of copper ribbon wound flatwise, often 
into a disc-like shape, and insulated by tape or strips of other 
material intervening between the successive turns. 

Coils, Compensating. Kxtra coils on the field magnets of dyna- 
mos or motors, which coils are in series with the armature wind- 
ings for the purpose of keeping the voltage constant. In compound 
wound machines the regular series- wound coil is thus termed. In 
a separately excited dynamo a coil of the same kind in circuit with 
the armature may be used as a compensator. 

Coils, Henry's. An apparatus used in repeating a classic experi- 
ment in electro-magnetic induction, due to Prof. Henry. It consists 
in a number of coils, the first and last ones single, the intermediate 
ones connected in pairs, and one of one pair placed on the top of 
one of the next pair. On opening or closing the circuit of an end 
coil the induced effect goes through the series and is felt in the cir- 
cuit of the other end coil. Prof. Henry extended the series so as 
to include seven successive inductions, sometimes called induc- 
tions of the first, second, third and other orders. Frequently 
ribbon coils (see Coil, Ribbon,) arc used in these experiments. 

Coils, Sectioned. A device for prolonging the range of mag- 
netic attraction. It consists of a series of magnetizing coils trav- 
ersed by an iron plunger. As it passes through them, the current 



STANDARD KU'CXRICAI. DICTIONARY. 



139 



is turned off the one in the rear or passing to the rear and turned into 
the next one in advance. The principle was utilized in one of 

Page's electric motors about [850, and later by others. The port- 
electric railroad, q. v., utilizes the same principle. 

Collecting: Ring:. In some kinds of generators instead of the 
commutator a pair of collecting rings of metal, insulated from the 
machine and from each other, are carried on the armature shaft. 
A brush, q. v.. presses on each, and the ^ 

circuit terminals connect to these two 
brushes. Such rings are employed often 
on alternating current generators, where 
the current does not have to be changed 
or commuted. Collecting rings with their 
brushes are used also where a current has 1 
to be communicated to a revolving coil or 
circuit as in the magnetic car wheel, the 
cut of which is repeated here. The coil 
of wire surrounding the wheel and rotat- 
ing with it has to receive current. This 
it receives through the two ^titionary 
brushes which press upon two insulated 
metallic rings, surrounding the shaft. 
The terminals of the coil connect one to 
each ring. Thus while the coil rotates it Fig . IO -. Magnetic Car 
constantly receives current, the brushes Wheel Showing Collecting 
being connected to the actuating circuit. Rings and Brushhs. 

Collector. a A name for the brush, q. v., in mechanical 
electric generators, such as dynamos, a pair of which collectors or 
brushes press on the commutator or collecting rings, and take off 
the current. 

The pointed connections leading to the prime conductor on 
a static machine for collecting the electricity; often called combs. 
The points of the combs or collectors face the statically charged 
rotating glass plate or cylinder of the machine. 

Colombin. The insulating material between the carbons in a 
Jablochkoff candle or other candle of that type. Kaolin was origin- 
ally used. Later a mixture of two parts calcium sulphate (plaster 
of Pari- and one part barium sulphate (barytes) was substituted. 

colombin was three millimeters (.12 inch) wide, and two 
millimet h thick. See Candle \Jablochkofi 

Column, Electric. An old name for the voltaic pile, made up 
of copper and zinc, with flannel discs, wet with salt 

or dilute acid, between each pair of plat 




140 



STANDARD ELECTRICAL DICTIONARY. 



Comb. A bar from which a number of teeth project, like the 
teeth of a comb. It is used as a collector of electricity from the 
plate of a frictional or influence electric machine; it is also used in 
a lightning arrester to define a path of very high resistance but of 
low self-induction, for the lightning to follow to earth. 

Communicator. The instrument by which telegraph signals 
are transmitted is sometimes thus termed. 

Commutator. In general an apparatus for changing. It IS 

on electric current generators, and motors, and on induction coils, 
and elsewhere, for changing the direction of currents, and 18 01 ■ 
great variety of types. 
Synonym — Commuter (but Little used , 





□ 




-■r:y 




































Fip. 106. DYNAMO ok Motor Commutator. 

Commutator Bars. The metallic segments of a dynamo or 
motor commutator. 

Commutator, Flats in. A wearing away or lowering in level of 
one or more metallic segments of a commutator. They are prob- 
ably due in many cases to sparking, set up by periodic springing in 
the armature mounting, or by defective commutator connections. 

Commutator of Current Generators and Motors. In general 
a cylinder, formed of alternate sections of conducting and non-con- 
ducting material, running longitudinally or parallel with the axis. 
Its place is on the shaft of the machine, so that it rotates therewith. 
Two brushes, q. v., orpieces of conducting material, press upon its 
surface. 

As a part ot electric motors and generators, its function is to 
collect the currents produced by the cutting of lines of force so as 
to cause them all to concur to a desired result. The cut shows 




STANDARD ELECTRICAL DICTIONARY. 141 

the simplest form of commutator, one with 
but two divisions. Its object may be to enable 
a current ot constant direction to be taken 
from a rotating armature, in which the cur- 
rents alternate or change direction once in Fig. 107. Section of 
each rotation. It is carried by the shaft A of Split Ring Commutator, 
the armature and roiates with "it. It consists WITH Brushes - 

of two leaves, S N. to which the terminals of the armature arc con- 
nected. Two springs, // ' // ", the terminals of the outer circuit, press 
against the leaves. The springs which do this take off the 
current. It is so placed, with reference to the springs and armature, 
that just as the current changes in direction, each leaf changes 
from one spring to the other. Thus the springs receive constant 
direction currents. The changing action of this commutator 
appears in its changing the character of the current from alternat- 
ing to constant. Were two insulated collecting rings used instead 
of a commutator, the current in the outer circuit would be an 
alternating one. On some dynamos the commutator has a very 
large number of leaves. 

Taking the Gramme ring armature, there must be as many divi- 
sions of the commutator as there are connections to the coils. 
In this case the function of the commutator is simply to lessen 
friction, for the brushes could be made to take current from the 
coils directly outside of the periphery of the ring. 

Commutator, Split Ring. A two-division commutator for a 
motor; it consists of two segments of brass or copper plate, bent to 
arcs of a circle, and attached to an insulating cylinder. They are 
mounted on the revolving spindle, which carries the armature, and 
acts as a two part commutator. For an example of its application, 
sec Armature y Revolving y Page's. (See also Fig. 107.) 

Compass. An apparatus for utilizing the directive force of the 
earth upon the magnetic needle. It consists of a circular case, 
within which is poised a magnetized bar of steel. This points 
approximately to the north, and is used on ships and elsewhere to 
constantly show the direction of the magnetic meridian. Two 
general types are used. In one the needle is mounted above a 
fixed '' card" or dial, on which degrees or points of the compass, 
q. v., arc inscribed. In the other thecard is attached to the needle 
and rotates with it. The latter represents especially the type 
known as the mariner's compass. (Sec Compass, Mariner* s Com* 
Spirit, and other titles under compass, also Magnetic 

-magnetic Elements. ) The needle in good compasses carries 
for a bearing at its centre, a little agate enp, and a sharp brass pin is 
■int of support. 

Compass, Azimuth. A compass with Bights on one of its diam- 

1 in determining the magnetic bearing of objects. 



142 



STANDARD ELECTRICAL DICTIONARY. 



Compass Card. The card in a compass; it is circular in shape, 
and its centre coincides with the axis of rotation of the magnetic 
needle; on it are marked the points of the compass, at the ends 
generally of star points. (See Compass, Points of thc. ) It may be 
fixed, and the needle may be poised above it, or it may be attached 
to the needle and rotate with it. 

Compass, Declination. An instrument by which the mag- 
netic declination of any place may be determined. It is vir- 
tually a transit instrument and 
compass combined, the teles- 
cope surmounting the latter. In 
the instrument shown in the 
cut, L is a telescope mounted bv 
is, A', in raised journals 
with vernier. A', and are .r, lor 
reading its vertical angle, with 
Level n. The azimuth circle, 
[K /\\ is fixed. A vernier, /' is 

carried by the box, . /, />', and 
both turn with the teles 

ry light Lozenge-ehaped 
magnetic needle, a t by is pivoted 

in the exact centre of the 
graduated circles. Q A', and M. 
The true meridan is determined 
by any convenient astronomical 
method, and the telescope is 
used for the purpose. The vari- 
ation of the needle from the 
meridian thus determined gives 
Fig. 108. Declination Compass. t hc magnetic declination. 

Compass, Inclination. A magnetic needle mounted on a hori- 
zontal axis at its centre of gravity, so as to be free to assume thc 
dip, or magnetic inclination, when placed in the magnetic meridian. 
It moves over the face of a vertical graduated circle, and the frame 
also carries a spirit level and graduated horizontal circle. In use 
the frame is turned until the needle is vertical. Then the axis 
of suspension of the needle is in the magnetic meridian. The 
vertical circle is then turned through 90 of thc horizon, which 
brings the plane of rotation of the needle into the magnetic merid- 
ian, when it assumes the inclination of the place. 

Compass, Mariner's. A compass distinguished by the card 
being attached to and rotating with the needle. A mark, the " lub- 
ber's mark " of the sailors is made upon the case. This is placed 
so that the line connecting it, and the axis of rotation of the card is 
exactly in a plane, passing through the keel of thc ship. Thus 




^m^^Tx «*«*<3«>-\.>'m> 



STANDARD ELECTRICAL DICTIONARY 



H3 



however the ship may be going, the point (,){ the card under or in 
line with the "lubber's mark," shows how the ship is pointing. 
The ease of the mariner's compass is often bowl-shaped and 




Fig. ioq. Mariner's Compass. 

mounted in gimbals, a species of universal joint, so as to be always 
horizontal. (See Compass, Spirit — Gimbals.) 

Compass, Points of the. The circle of the horizon may be and 
is best referred to angular degrees. It has also been divided into 
thirty-two equiangular and named points. A point is n%°. The 
names of the points are as follows : Norths North by East, North 
North-east ', North-east by North, North-east, North-east by East, 
East North-east, East by North, East, East by South, East 
South-east, South-east by East, South-east, South-east by South, 
South South-east, South by East, South, South by West, South 
South-west, South-west bv South South-west, South-west by West, 
\ West by South, West, West by North, West 
Nortr- rth-west by West, North-west, North West by 

North, North North-west. North by West. They are indicated 
bv their initials as N. N. W., North North-west, N. by W., North 
by West. 

Compass, Spirit. A form of mariner's compass. The bowl or 
case is hermetically scaled and filled with alcohol or other non- 
ttg liquid. The compass card is made with hollow compart- 
ments so as nearly to float. In this way the friction of the pivot 
or point of support is greatly diminished, and the compass is far 
more sensitive. 

Compass, Surveyor's. A species of theodolite ; a telescope 
with oollimation lines, mounted above B com; fco be appli- 

cable f<»r magnetic Bui - use is to be disoonraged on account 

of the inaccuracy and changes in declination of the magnetic needle. 



144 STANDARD ELECTRICAL DICTIONARY. 

Compensating Resistances. In using a galvanometer shunt 
the total resistance of the circuit is diminished so that in some 
cases too much current flows through it ; in such case additional 
resistance, termed as above, is sometimes introduced in series. The 
shunt in parallel with the galvanometer is thus compensated for, 
and the experimental or trial circuit does not take too much current. 

Complementary Distribution. Every distribution of electricity 
has somewhere a corresponding distribution, exactly equal to it, of 
opposite electricity ; the latter is the complimentary distribution 
to the first, and the first distribution is also complimentary t<> it. 

Component. A force may always be represented diagrammetic- 
ally by a straight line, terminating in an arrow-head to indicate 
the direction, and of length to represent the intensity of the force. 
The line may always be assumed to represent the diagonal of a 
parallelogram, two of whose sides are represented by lines starting 
from the base of the arrow, and of length fixed by the condition 
that the original force shall be the diagonal of the parallelogram 
ofwhich they are two contiguous sides ; such lines are called compo- 
nents, and actually represent forces into which the original force 
may always be resolved. The components can have any direction. 
Thus the vertical component of a horizontal force is zero ; its hori- 
zontal component is equal to itself. Its 4,5 J component is equal to 
the square root of one-half of its square. 

Condenser. An appliance for storing up electrostatic charges; 
it isalso called a static accumulator. The- telegraphic condeu 
consists of a box packed full of sheets of tinfoil. Between every two 
sheets is a sheet of paraffined paper, or of mica. The alternate 

sheets of tinfoil are connected together, and each set has its own 

binding post. (vScc Accumulator, Electrostatic.) 

Condenser, Sliding. An apparatus representing a Leydcnjar 
whose coatings can be slid past each other. This diminishes or 
increases the facing area, and consequently in almost exactly simi- 
lar ratio diminishes or increases the capacity of the condenser. 

Conductance. The conducting power of a given mass of speci- 
fied material of specified shape and connections. Conductance 
varies in cylindrical or prismatic conductors, inversely as the length, 
directly as the cross-section, and with the conductivity of the 
material. Conductance is an attribute of any specified conductor, 
and refers to its shape, length and other factors. Conductivity 1^ 
an attribute of any specified material without direct reference to 
its shape, or other factors. 

Conduction. The process or act of conducting a current. 

Conductivity. The relative power of conducting the electric 
current possessed by different substances. A path for the current 



STANDARD ELECTRICAL DICTIONARY. 145 

through the ether is opened by the presence of a body of 
proper quality, and this quality, probably corelated to opacity, 
is termed conductivity. There is no perfect conductor, all offer 
some resistance ) q. v., and there is hardly any perfect non-conduc- 
tor. It is the reverse and reciprocal of resistance. 

Conductivity, Specific. The reciprocal of specific resistance. 
i^See Resistance^ Specific.) 

Conductivity, Unit of. The reciprocal of the ohm ; it is a 

more logical unit, but has never been generally adopted ; as a 
name the title viho (or ohm written backwards) has been suggested 
by Sir William Thomson, and provisionally adopted. 

Conductivity, Variable. The conductivity for electric currents 
of conductors varies with their temperature, with varying magnet- 
ization, tension, torsion and compression. 

Conductor. In electricity, anything that permits the passage 
of an electric current. Any disturbance in the ether takes the 
form of waves because the ether has restitutive force or elasticity. 
In a conductor, on the other hand, this force is wanting ; it opens 
a path through the ether and a disturbance advances through it 
from end to end with a wave front, but with no succession of waves. 
This advance is the beginning of what is termed a current. It is, 
by some theorists, attributed to impulses given at all points along 
the conductor through the surrounding ether, so that a current is 
not merely due to an end thrust. If ether waves preclude a cur- 
rent on account of their restitutive force, ether waves cannot be 
maintained in a conductor, hence conductors should be opaque to 
Light, for the latter is due to ether waves. This is one of the more 
practical every day facts brought out in Clerk Maxwell's electro- 
magnetic theory of light. The term conductor is a relative one, as 
except a vacuum there is probably no substance that has not some 
conducting power. For relative conducting power, tables of con- 
ductivity, q. v., should be consulted. The metals beginning with 
silver are the best conductors, glass is one of the worst. 

Conductor, Anti = Induction. A current conductor arranged to 
avoid induction from other lines. Many kinds have been invented 
and made the subject of patents. A fair approximation may be 
attained by using a through metallic circuit and twisting the wires 
compo>ing it around each other. Sometimes concentric con- 
ductors, one a wire and the other a tube, are used, insulated, one 
acting as return circuit for the other. 

Conductor, Conical. A prime conductor of approximately 
conical shape, but rounded on all points and angles. lis potential 

is highest at the point. 



146 STANDARD ELECTRICAL DICTIONARY. 

Conductor, Imbricated. A conductor used in dynamo arma- 
tures for avoiding eddy currents, made by twisting together two or 
more strips of copper . 

Conductor, Prime. A body often cylindrical or spherical in 
shape, in any case w T ith no points or angles, but rounded every- 
where, whose surface, if the conductor itself is not metallic 
made conducting by tinfoil or gold leaf pasted over it. It is 
supported on an insulating stand and is used to collect or receive 
and retain static charges of electricity. 

Conductors, Equivalent. Conductors of identical resistance. 
The quotient of the length divided by the product of the conduc- 
tivity and cross-section must be the same in each, if each is of 
uniform diameter. 

Conjugate, adj. Conjugate coils or conductors are coils placed 
in such relation that the lines of force established by one do not 
pass through the coils of the other. Hence variations of current in 
one produce no induced currents in the other. 

Connect, v. To bring two ends of a conductor together, or to 
bring one end of a conductor in connection with another, or in any 
way to bring about an electrical connection. 

Connector. A sleeve with screws or other equivalent device for 
securing the ends of wires in electrical contact. A binding-post, 
q. v., is an example. Sometimes wire spring-catches are used, the 
general idea being a device that enables wires t<> be connected or 
released at will without breaking off or marring their cuds. The 
latter troubles result from twisting wires together. 

Consequent Poles. A bar magnet is often purposely or acci- 
dentally magnetized so as to have both ends of the same polarity, 
and the center of opposite polarity. The center is said to com- 
prise two consequent poles. ^Scc Magnet % Anomalous.} 

Conservation of Electricity. As every charge of electricity 
has its equal and opposite charge somewhere, near or far, more or 
less distributed, the sum of negative is equal always to the sum of 
positive electrical charges. For this doctrine the above title was 
proposed by Lippman. 

Contact Breaker. Any contrivance for closing a circuit, and 
generally for opening and closing in quick succession. An old and 
primitive form consisted of a very coarsely cut file. This was con- 
nected to one terminal, and the other terminal was drawn over its 
face, making and breaking contact as it jumped from tooth to tooth. 
(See Circuit Breaker— do. Automatic, etc— do, Wheel—do* Fcn- 
dulum.) 



STANDARD ELECTRICAL DICTIONARY. 147 

Contact, Electric. A contact between two conductors, such 
that a current can flow through it. It may be brought about by 
simple touch or impact between the ends or terminals of a circuit, 
so netimes called a dotting contact, or by a sliding or rubbing of 
one terminal on another, or by a wheel rolling on a surface, the 
wheel and surface representing the two terminals. 

There are various descriptions of contact, whose names are self- 
explanatory. The term is applied to telegraph line faults also, and 
under this, includes different descriptions of contact with neighbor- 
ing lines, or with the earth. 

Contact Electricity. When two dissimilar substances are 
touched they assume different electric potentials. If conductors, 
their entire surfaces are affected; if dielectrics, only the surfaces 
which touch each other. i^See Contact Theory. .) 

Contact Faults. A class of faults often called contacts, due to 
contact of the conductor of a circuit with another conductor. A 
full or metallic contact is where practically perfect contact is estab- 
lished ; a partial contact and intermittent contact are self-explana- 
tory. 

Contact Point, A point, pin or stud, often of platinum, 
arranged to come in contact with a contact springs q. v., or another 
contact point or surface, under any determined conditions. 

Contact Potential Difference. The potential difference estab- 
lished by the contact of two dissimilar substances according to the 
contact theory, q. v. 

Contact Series. An arrangement or tabulation of substances 
in pairs, each intermediate substance appearing in two pairs, as the 
last member of the first, and first member of the succeeding pair, 
with the statement of the potential difference due to their contact, 
the positively electrified substance coming first. The following 
table of some contact potentials is due to Ayrton and Perry : 

CONTACT SERIES. 

Diffei 'Potential in Volts* 

Zinc » mwjr> Iron 1 i( - 

r I 2IO r, 140 

id 1 Copper 1 

Lead. , Copper 1 ^ 

Tin °° 9 Platinum . 23 ° 

Tin ' ^ ^ Platinum 1 

Iron i '3.3 Carbon 1 ^ 

The sum of these differefl £9, which is the contact poten- 

tial between zinc and carbon. 



148 STANDARD ELECTRICAL DICTIONARY. 

Volla's Law refers to this and states that— 

The difference of potential produced by the contact of any t:co 
substances is equal to the sum of the differences of potentials bet:. 
the intervening substances i?i the coJitact series. 

It is to be remarked that the law should no longer be restricted 
to or stated only for metals. 

Contact=spring. A spring connected to one lead of an electric 
circuit, arranged to press against another spring, or contact point, 
q. v., under any conditions determined by the construction of the 
apparatus. (See Bell, Electric — Coil, Induction.) 

Contact Theory. A theory devised to explain electrification, 
the charging of bodies by friction, or rubbing, and the production 
of current by the voltaic battery. It holds that two bodies, by mere 
contact become oppositely electrified. If such contact is increased 

in extent by rubbing together, the intensity of their electrification 
is increased. This electrification is accounted for by the assumption 
of different kinetic energy, or energy of molecular motion, | 
by the two bodies ; there being a loss and gain of energy, on the two 
sides respectively, the opposite electrifications are the result. T lien 
when separated, the two bodies come apart oppositely electrified. 

The above accounts for the frictional production of electricity. 
In the voltaic battery, a separation of the atoms of hydrogen and 
oxygen, and their consolidation into molecules occurs, and to such 
separation and the opposite electrification of the electrodes !>y 
the oxygen and hydrogen, the current is attributed, because the 
hydrogen goes to one electrode, and the oxygen to the other, each 
giving up or sharing its own charge with the electrodes to which it 
goes. If zinc is touched to copper, the zinc is positively and the 
copper negatively electrified. In the separation of hydrogen and 
oxygen, the hydrogen is positively and the oxygen negatively elec- 
trified. In the battery, the current is due to the higher contact differ- 
ence of oxygen and hydrogen compared to that between zinc and 
copper. It will be seen that the two contact actions in a battery work 
against each other, and that the current is due to a differential contact 
action. The zinc in a battery is electrified negatively because the 
negative electrification of the oxygen is greater in amount than its 
own positive electrification due to contact with the copper. 

Contractures. A muscular spasm or tetanus due to the passage 
of a current of electricity; a term in electro-therapeutics. 

Controlling Field. The magnetic or electro-magnetic field, 
which is used in galvanometers to control the magnetic needle, 
tending to restore it to a definite position whenever it is turned 
therefrom. It may be the earth's field or one artificially produced. 

Controlling Force. In galvanometers and similar instruments, 



STANDARD ELECTRICAL DICTIONARY. 149 

the force used to brine: the needle or indicator back to zero. (See 
Controlling Field —Electro-Magnetic Control -Gravity Control- 
Magnetic Control -Spring Control.) 

Convection, Electric. The production of blasts or currents of 
air (convection streams) from points connected to statically charged 

conductors. The term is sometimes applied to electric convection 
of heat. (See Convection of Heat, Electric^ 

Convection, Electrolytic. The resistance of acidulated water as 
a true conductor is known to be very, almost immeasurably, high. 
As an electrolytic, its resistance is very much lower. Hence the 
current produced between immersed electrodes is theoretically 
almost null, unless the difference of potential between them is high 
enough to decompose the liquid. Yet a feeble current too great for 
a true conduction current is sometimes observed when two elec- 
trodes with potential difference too low to cause decomposition are 
immersed in it. Such' a current is termed an electrolytic convec- 
tion current. It is supposed to be due to various causes. Some 
attribute it to the presence of free oxygen from the air, dissolved in 
the water with which the hydrogen combines. Others attribute it 
to the diffusion of the gases of decomposition vn the solution; 
others assume a partial polarization of the molecules without 
decomposition. Other theories are given, all of which are unsatis- 
factory. The term is due to Helmholtz. 

Convection of Heat, Electric. The effect of a current upon the 
distribution of heat in an unevenly heated conductor. In some, 
such as copper, the current tends to equalize the varying tempera- 
tures; the convection is then said to be positive, as comparable to 
that of water flowing through an unequally heated tube. In others, 
such as platinum or iron, it is negative, making the heated parts 
hotter, and the cooler parts relatively cooler. 

The effect of the electric current in affecting the distribution of 
heat in unequally heated metal (Thomson's effect, q. v.), is some- 
times so termed. If a current passes through unequally heated 
iron it tends to increase the difference of temperature, and the con- 
vection is negative; in copper it tends to equalize the temperature, 
and the convection is positive. 

Converter. An induction coil used with the alternating current 
for changing potential difference and inversely therewith the avail- 
able current. They generally lower the potential, and increase the 
current, and are placed between the primary high potential Bystem 

that connects the houses with the central station, and the second- 
ary low potential system within the houses. A converter consists 

of a core of thin iron sheets, wound with :\ tine primary coil of 
many convolutions, and a ^ I of few convolutions. 



i5o 



vSTANDARD ELECTRICAL DICTIONARY 



The ratio of convolutions gives the ratio of maximum potential 
differences of their terminals between the primary and secondary 




Fip. no. Fhkranti's C y I 

coils. The coil may l>o jacketed with iron to increase the per- 
meance. (See Alternating c urrent System.) 



M Wm 



Fig. in. Swinburne's Hedgehog Transformer. 

Coordinates, System of. A system for indicating the posi- 
tion of points in space by reference to fixed lines, intersecting at ■ 
determined and arbitrary point O, termed the origin of co-ordinates. 
In plane rectangular co-ordinates two lines are drawn through the 
origin, one horizontal, termed the axis of abscissas, or axis of X. 
All distances measured parallel to it, if unknown, arc indicated by 
A', and are termed abscissas. The other axis is vertical, and is termed 



STANDARD ELECTRICAL DICTIONARY. 151 

the axis of ordinate*, or axis of Y. All distances measured 
parallel to it, if unknown, arc indicated by v and arc termed ordi- 
natcs. Thus by naming its abscissa and ordinate a point has its 
position with reference to the axes determined, and by indicating 
the relation between a point, line or curve, and a system of abscissas 
andordinates, the properties of a line or curve can be expressed alge- 
braically. Co-ordinates may also be inclined to each other at any 
other angles, forming oblique co-ordinates; relations may be ex- 
pressed partly in angles referred to the origin as a centre, giving 
polar co-ordinates. For solid geometry or calculations in three 
dimensions, a third axis, or axis of Z, is used, distances parallel to 
which if unknown are indicated by ~. 







X 



Fig-. 112. Axes of Co-ordinates. 

Cooling: Box. In a hydroelectric machine, q. v., a conduit 
or chest through which the steam passes on its way to the nozzles. 
IN object i^ to partially condense the steam soasto charge it with 
water vesicles whose friction against the sides of the nozzles pro- 
dnces the electrification: 

Copper. A metal : one of the elements. Symbol, Cu ; atomic 
weight, 63.5; equivalent, 63.5 and 31.75; valency, 1 and 2; 

specific gravity, .s.96. It is a conductor of electricity, whose 
Conductivity IS liable to vary greatly on account of impnrit: 

Alinealed. Hard drawn. 
Relative resistance Silver 1 , i.< 

Mice, 1 .634 microhms. 



152 



STANDARD ELECTRICAL DICTIONARY. 



Resistance of a wire at o° C. (32 F.), 



(a) 1 foot long, weighing 1 grain, 
(5) 1 foot long, 1-1000 inch thick, 

(c) 1 meter long, weighing 1 gram, 

(d) 1 meter long, 1 millimeter thick, 



Annealed. Hard Drawn. 
.2041 ohms. .2083 ohms. 
9.831 » 

.1453 " 
.02081 " 

microhm. 

.6433 



9.612 
.1424 
.02034 " 
microhm. 
Resistance of 1 inch cube at o°C.(32° F.) .6292 
Percentage of resistance change, 

per o° C. (i.8° F.) at about 20 C. (68° F.) 0.388 per cent. 
Electro-chemical Equivalent (Hydrogen = .0105) Cuprous .6667 

Cupric .3334 
In electricity it has been very extensively used as the negative 
plate of voltaic batteries. It has its most extensive application as 
conductors for all classes of electrical leads. 

Copper Bath. A solution of copper used for depositing the 
metal in the electroplating process. For some metals, such as zinc 
or iron, which decompose copper sulphate solution, special baths 
have to be used. 

The regular bath for copper plating is the following : 

To water acidulated with 8 to 10 percent, of sulphuric acid as much 
copper sulphate is added as it will take up at the ordinary tempera- 
ture. The saturated bath should have a density of 1.21. It is 
used cold and is kept in condition by the use of copper anodes, or 
fresh crystals may be added from time to time. 

For deposition on zinc, iron, tin and other metals more electro- 
positive than copper, the following baths may be used, expressed 
in parts by weight : 





Iron and Steel. 


Tin, 
Cast 
Iron 
and 
Zinc. 


Zinc. 




Cold. 


Hot. 




Sodium Bisulphate, - , - 
Potassium Cyanide, - 
Sodium Carbonate, - 
Copper Acetate, - - 
Aqua Ammonise, - 
Water, - - - 


500 
500 

IOOO 
475 
35o 

2500 


200 
700 
500 
500 
300 
2500 


300 
500 

350 

200 

2500 


IOO 
700 

450 

I50 

2500 



These are due to Roseleur. 

Copper Stripping Bath. There is generally no object in strip- 
ping copper from objects. It can be done with any of the regular 



STANDARD ELECTRICAL DICTIONARY. 153 

copper baths using the objects to be stripped as anode. The dan- 
ger of dissolving the base itself and thereby injuring the article and 
spoiling the bath is obvious. 

Cord Adjuster. A device for shortening or lengthening the 
flexible cord, or flexible wire supplying the current, and by which an 
incandescent lamp is suspended. It often is merely a little block of 
wood perforated with two holes through which the wires pass, and 
in which they are retained in any desired position by friction and 
their own stiffness. 




Fig. 113. Flexible Cord Adjuster. 

Cord, Flexible. A pair of flexible wire conductors, insulated 
lightly, twisted together and forming apparently a cord. They are 
used for minor services, such as single lamps and the like, and are 
designated according to the service they perform, such as battery 
cords, dental cords (for supplying dental apparatus) and other titles. 

Core, (a) The conductor or conductors of an electric cable. (See 
Cable Core.) 

(b) The iron mass, generally central in an electro-magnet or 
armature, around which the wire is coiled. It acts by its high per- 
meance to concentrate or multiply the lines of force, thus main- 
taining a more intense field. (See Armature — Magnet, Electro— 
Magnet, Field— Core, Laminated). In converters or transformers 
(See Converter) it often surrounds the wire coils. 

Core=discs. Discs of thin wire, for building up armature cores. 
(See Laminated Core.) The usual form of core is a cylinder. A 
number of thin discs of iron are strung upon the central shaft 
and pressed firmly together by end nuts or keys. This arrange- 
ment, it will be seen, gives a cylinder as basis for winding the wire on. 

Core=discs, Pierced. Core-discs for an armature of dynamo or 
motor, which are pierced around the periphery. Tubes of insulat- 
ing material pass through the peripheral holes, and through these 
the conductors or windings are carried. The conductors are thus 
embedded in a mass of iron and are protected from eddy currents, 
and they act to reduce the reluctance of the air gaps. From a 



154 



STANDARD ELECTRICAL DICTIONARY. 



mechanical point of view they are very good. For voltages over 
ioo they are not advised. 
Synonym — Perforated Core-discs. 

Core=discs, Segmental. Core-discs made in segments, which 
are bolted together to form a complete disc or section of the core. 




Fig. 114. Pierced or Perforated Core-disc. 

The plan is adopted principally on large cores. The discs thus made 
up are placed together to form the core exactly as in the case of 
ordinary one piece discs. 

Core=discs, Toothed. Core-discs of an armature of a dynamo 
or motor, which discs are cut into notches on the periphery. These 
are put together to form the armature 
core, with the notches corresponding 
so as to form a series of grooves in 
which the wire winding is laid. This 
construction reduces the actual air- 
gaps, and keeps the wires evenly spaced. 
Distance-pieces of box- wood, m, m> 
are sometimes used to lead the wires 
at the ends of the armature. 

Core, Laminated. A core of an 
armature, induction coil or converter 
or other similar construction, which is 
Fig. 115. Toothed Core-disc. made up of p l ates i nsu l a ted more or 

less perfectly from each other. The object of lamination is to pre- 
vent the formation of Foucault currents. (See Currents, Foucault.) 
As insulation, thin shellacked paper may be used, or sometimes 
the superficial oxidation of the plates alone is relied on. The 




STANDARD ELECTRICAL DICTIONARY. 155 

plates, in general, are laid perpendicular to the principal convolu- 
tions of the wire, or parallel to the lines of force. The object is to 
break up currents, and such currents are induced by the variation 
in intensity of the field of force, and their direction is perpendicular 
to the lines of force, or parallel to the inducing conductors. 

A core built up of core discs is sometimes termed a radially 
laminated core. Made up of ribbon or wire wound coil fashion, it 
is termed a tangentially laminated core. 

Core Ratio. In a telegraph cable the ratio existing between 
the diameter of the conducting core and the insulator. To get a 
ratio approximately accurate in practical calculations, the diameter 
of the core is taken at 5 per cent, less than its actual diameter. 
The calculations are those referring to the electric constants of the 
cable, such as its static capacity and insulation resistance. 

Core, Ribbon. For discoidal ring-shaped cores of armatures, 
iron ribbon is often used to secure lamination and prevent Foucault 
currents. 

Synonym — Tangentially Laminated Core. 

Core, Ring. A core for a dynamo or motor armature, which 
core forms a complete ring. 

Core, Stranded. In an electric light cable, a conducting core 
made up of a group of wires laid or twisted together. 

Core, Tubular. Tubes used as cores for electro-magnets. For 
very small magnetizing power, tubular cores are nearly as efficient 
as solid ones in straight magnets, because the principal reluctance 
is due to the air-path. On increasing the magnetization the tubular 
core becomes less efficient than the solid core, as the reluctance of 
the air-path becomes proportionately of less importance in the 
circuit. 

Corpusants. The sailors' name for St. Elmo's Fire, q. v. 

Coulomb. The practical unit of quantity of electricity. It is 
the quantity passed by a current of one ampere intensity in one 
second. It is equal to 1-10 the C. G. S. electro-magnetic unit of 
quantity, and to 3,000,000,000 C. G. S. electrostatic units of 
quantity. It corresponds to the decomposition of .0935 milligrams 
of water, or to the deposition of 1.11815 milligrams of silver. 

Coulomb's Laws of Electrostatic Attraction and RepuU 
sion. 1. The repulsions or attractions between two electrified bodies 
are in the inverse ratio of the squares of their distance. 

2. The distance remaining the same, the force of attraction or 
repulsion between two electrified bodies is directly as the product 
of the quantities of electricity with which they are charged. 



156 STANDARD ELECTRICAL DICTIONARY. 

Counter, Electric* A device for registering electrically, or by 
electro-magnetic machinery, the revolutions of shafts, or any other 
data or factors. 

Counter - electro=motive Force. A potential difference in a 
circuit opposed to the main potential difference, and hence, 
resisting the operation of the latter, and diminishing the current 
which would be produced without it. It appears in electric 
motors, which, to a certain extent, operate as dynamos and reduce 
the effective electro-motive force that operates them. It appears 
in the primary coils of induction coils, and when the secondary 
circuit is open, is almost equal to the main electro-motive force, so 
that hardly any current can go through them under such condi- 
tions. It appears in galvanic batteries, when hydrogen accumulates 
on the copper plate, and in other chemical reactions. A secondary 
battery is charged by a current in the reverse direction to that which 
it would normally produce. Its own potential difference then 
appears as a counter-electro-motive force. 

Synonym— Back Electro-motive Force. 

Counter=electro=motive Force of Polarization. To decom- 
pose a solution by electrolysis, enough electro-motive force is 
required to overcome the energy of composition of the molecule 
decomposed. A part of this takes the form of a counter-electro- 
motive force, one which, for a greater or less time would maintain 
a current in the opposite direction if the original source of current 
were removed. Thus in the decomposition of water, the electrodes 
become covered, one with bubbles of oxygen, the others with bubbles 
of hydrogen; this creates a counter E. M. F. of polarization. In a 
secondary battery, the working current may be defined as due to 
this cause. 

Synonym — Back Electro-motive Force of Polarization. 

Couple. Two forces applied to different points of a straight line, 
when opposed in direction or unequal in amount, tend to cause 
rotation about a point intermediate between their points of appli- 
cation and lying on the straight line. Such a pair constitute a 
couple. 

Couple, Voltaic or Galvanic. The combination of two elec- 
trodes, and a liquid or liquids, the electrodes being immersed 
therein, and being acted on differentially by the liquid or liquids. 
The combination constitutes a source of electro-motive force and 
consequently of current. It is the galvanic or voltaic cell or bat- 
tery. (See Battery, Voltaic— Contact Theory — Electro-motive Force ;, 
— Electro-motive Series.) 

Coupling. The joining of cells of a galvanic battery, of dynamos 
or of other devices, so as to produce different effects as desired. 



STANDARD ELECTRICAL DICTIONARY- 157 

Couple, Astatic. An astatic couple is a term sometimes applied 
to astatic needles, q. v. 

C. P. (a) An abbreviation of or symbol for candle power, q, v. 

(b) An abbreviation of chemically pure. It is used to indicate 
a high degree of purity of chemicals. Thus, in a standard Daniell 
battery, the use of C. P. chemicals may be prescribed or advised. 

Crater. The depression that forms in the positive carbon of a 
voltaic arc. (See Arc , Voltaic.) 

Creeping. A phenomenon of capillarity, often annoying in 
battery jars. The solution, by capillarity, rises a little distance up 
the sides, evaporates, and as it dries more creeps up through it, 
and to a point a little above it. This action is repeated until a 
layer of the salts may form over the top of the vessel. To avoid it, 
paraffine is often applied to the edges of the cup, or a layer of oil, 
often linseed oil, is poured on the battery solution, 

Crith. The weight of a litre of hydrogen at o° C. (32 P.), and 
760 mm. (30 inches) barometric pressure. It is .0896 grams. The 
molecular w T eight of any gas divided by 2 and multiplied by the 
value of the crith, gives the weight of a litre of the gas in question. 
Thus a litre of electrolytic gas, a mixture of two molecules of hydro- 
gen for one of oxygen, with a mean molecular weight of 12, 
weighs 12/2 X. 0896 or .5376 gram. 

Critical Speed, (a) The speed of rotation at which a series 
dynamo begins to excite its own field. 

(b) In a compound wound dynamo, the speed at which the same 
potential is generated with the full load being taken from the 
machine, as would be generated on open circuit, in which case the 
shunt coil is the only exciter. The speed at which the dynamo is 
self-regulating. 

(c) In a dynamo the rate of speed when a small change in the 
speed of rotation produces a comparatively great change in the 
electro-motive force. It corresponds to the same current (the 
critical current) in any given series dynamo. 

Cross, (a) A contact between two electric conductors ; qualified 
to express conditions as a weather cross, due to rain, a swinging 
cross when a wire swings against another, etc. 

[b) vb. To make such contact. 

Cross=Connecting Board. A special switch board used in 
telephone exchanges and central telegraph offices. Its function 
is, by plugs and wires, to connect the line wires with any desired 
section of the main switchboard. The terminals of the lines as 
they enter the building are connected directly to the cross-con- 
necting board. 



158 



vSTANDARD ELECTRICAL DICTIONARY. 



Cross Connection. A method of disposing of the effects of 
induction from neighboring circuits by alternately crossing the 
two wires of a metallic telephone circuit, so that for equal inter- 
vals they lie to right and left, or one above and one below. 

Crossing Wires. The cutting out of a defective section in a 
telegraph line, by carrying two wires from each side of the defec- 
tive section across to a neighboring conductor, pressing it for the 
time into service and cutting the other wire if necessary. 

Cross=magnetizing Effect. A phase of armature interference. 
The current in an armature of a dynamo or motor is such as to 
develop lines of force approximately at right angles to those of 
the field. The net cross-magnetizing effect is such component of 
these lines, as is at right angles to the lines produced by the field 
alone. 

Cross=over Block. A piece of porcelain or other material 
shaped to receive two wires which are to cross each other, and hold 
them so that they cannot come in contact. It is used in wiring 
buildings, and similar purposes. (See Cleat, Crossing.) 

Cross Talk. On telephone circuits by induction or by contact 
with other wires sound effects of talking are sometimes received 
from other circuits ; such effects are termed cross talk. 

Crucible, Electric. A crucible for melting difficultly fusible 
substances, or for reducing ores, etc., by the electric arc produced 
within it. Sometimes the heating is due more to current incan- 
descence than to the action of an arc. 




Fig. 116. Electric Furnace or Crucible. 

Crystallization, Electric. Many substances under proper con- 
ditions take a crystalline form. The great condition is the passage 
from the fluid into the solid state. When such is brought about by 
electricity in any way, the term electric crystallization may be 
applied to the phenomenon. A solution of silver nitrate for 
instance, decomposed by a current, may give crystals of metallic 
silver. 



STANDARD ELECTRICAL DICTIONARY. 159 

Cup, Porous. A cup used in two-fluid voltaic batteries to 
keep the solutions separate to some extent. It forms a diaphragm 
through which diffusion inevitably takes place, but which is con- 
siderably retarded, while electrolysis and electrolytic convection 
take place freely through its walls. As material, unglazed pottery 
is very generally used. 

In some batteries the cup is merely a receptacle for the solid 
depolarizer. Thus, in the Leclanche battery, the cup contains the 
manganese dioxide and graphite in which the carbon electrode is 
embedded, but does not separate two solutions, as the battery only 
uses one. Nevertheless, the composition of the solution outside 
and inside may vary, but such variation is incidental only, and not 
an essential of the operation. 

Current. The adjustment, or effects of a continuous attempt at 
readjustment of potential difference by a conductor, q. v., connect- 
ing two points of different potential. A charged particle or body 
placed in a field of force tends to move toward the oppositely 
charged end or portion of the field. If a series of conduct- 
ing particles or a conducting body are held so as to be unable 
to move, then the charge of the field tends, as it were, to move 
through it, and a current results. It is really a redistribution 
of the field and as long as such redistribution continues a current 
exists. A current is assumed to flow from a positive to a negative 
terminal ; as in the case of a battery, the current in the outer cir- 
cuit is assumed to flow from the carbon to the zinc plate, and in 
the solution to continue from zinc to carbon. As a memoria 
technica the zinc may be thought of as generating the current 
delivering it through the solution to the carbon, whence it flows 
through the wire connecting them. (See Ohm's Law — Maxwell's 
Theory of Lighl — Conductor — Intensity. ) 

Current, After. A current produced by the animal tissue after 
it has been subjected to a current in the opposite direction for 
some time. The tissue acts like a secondary battery. The term is 
used in electro-therapeutics. 

Current, Alternating. Usually defined and spoken of as a cur- 
rent flowing alternately in opposite directions. It may be con- 
sidered as a succession of currents, each of short duration and of 
direction opposite to that of its predecessor. It is graphically 
represented by such a curve as shown in the cut. The horizon- 
tal line may denote a zero current, that is no current at all, or may 
be taken to indicate zero electro-motive force. The curve represents 
the current, or the corresponding electro-motive forces. The further 
from the horizontal line the greater is either, and if above the line the 
direction is opposite to that corresponding to the positions below the 
line. Thus the current is alternately in opposite directions, has periods 



160 STANDARD ELECTRICAL DICTIONARY. 

of maximum intensity, first in one and then in the opposite sense, 
and between these, passing from one direction to the other, is of 
zero intensity. It is obvious that the current may rise quickly in 
intensity and fall slowly, or the reverse, or may rise and fall irreg- 
ularly. All such phases may be shown by the curve, and a curve 
drawn to correctly represent these variations is called the character- 
istic curve of such current. It is immaterial whether the ordinates 
of the curve be taken as representing current strength or electro- 
motive force If interpreted as representing electro-motive force, the 
usual interpretation and best, the ordinates above the line are taken 
as positive and those below as negative. 
Synonyms — Reversed Current — Periodic Currents. 



360° 



Fig. 117. Characteristic Curve of Alternating Current. 

Current, Atomic. A unit of current strength used in Germany ; 
the strength of a current which will liberate in 24 hours (86,400 
seconds) one gram of hydrogen gas, in a water voltameter. The 
atomic current is equal to i.iii amperes. In telegraphic work the 
milliatom is used as a unit, comparable to the milliampere. The 
latter is now displacing it. 

Current, Charge. If the external coatings of a charged and 
uncharged jar are placed in connection, and if the inner coatings 
are now connected, after separating them they are both found to be 
charged in the same manner. In this process a current has been 
produced between the outside coatings and one between the inner 
ones, to which Dove has given the name Charge Current, and 
which has all the properties of the ordinary discharge current. 
(Ganot.) 

Current, Circular. A current passing through a circular con- 
ductor ; a current whose path is in the shape of a circle. 

Current, Commuted. A current changed, as regards direction 
or directions, by a commutator, q. v. , or its equivalent. 

Current, Constant. An unvarying current. A constant cur- 



STANDARD ELECTRICAL DICTIONARY. 161 

rent system is one maintaining such a current. In electric series, 
incandescent lighting, a constant current is employed, and the 
system is termed as above. In arc lighting systems, the constant 
current series arrangement is almost universal. 

Current, Continuous. A current of one direction only ; the 
reverse of an alternating current. (See Current \ Alternating,) 

Current, Critical. The current produced by a dynamo at its 
critical speed ; at that speed when a slight difference in speed pro- 
duces a great difference in electro-motive force. On the character- 
istic curve it corresponds to the point where the curve bends sharply, 
and where the electro-motive force is about two-thirds its maximum. 

_ Daniell Daniell 

Current, , T „ — or — — __ mjL A unit of current 

U. S. Siemens' Unit. 

strength used in Germany. It is the strength of a current pro- 
duced by one Daniell cell in a circuit of the resistance of one 
Siemens' unit. The current deposits 1.38 grams of copper per 
hour. It is equal to 1.16 amperes. 

Current, Demarcation. In electro-therapeutics, a current which 
can be taken from an injured muscle, the injured portion acting 
electro-negatively toward the uninjured portion. 

Current Density. The current intensity per unit of cross-sec- 
tional area of the conductor. The expression is more generally 
used for electrolytic conduction, where the current-density is 
referred to the mean facing areas of the electrodes, or else to the 
facing area of the cathode only. 

The quality of the deposited metal is intimately related to the 
current density. (See Burning '.) 

Proper Current Density for Electroplating — Amperes Per Square 

Foot of Cathode. — (Urquhart.) 

Copper, Acid Bath, - - - - - - 5.0 to 10.0 

" Cyanide Bath, ----- 3.0 " 5.0 

Silver, Double Cyanide, - 2.0 " 5.0 

Gold, Chloride dissolved in Potassium Cyanide, 1.0 " 2.0 

Nickel, Double Sulphate, - - - - 6.6 " 8.0 

Brass, Cyanide, - 2.0 " 3.0 

Current, Diacritical. A current, which, passing through a 
helix surrounding an iron core, brings it to one-half its magnetic 
saturation^ q. v. 

Current, Diaphragm. If a liquid is forced through a diaphragm, 
a potential difference between the liquid on opposite sides of the 
diaphragm is maintained. Electrodes or terminals of platinum 
may be immersed in the liquid, and a continuous current, termed 



162 STANDARD ELECTRICAL DICTIONARY. 

a diaphragm current, may be taken as long as the liquid is forced 
through the diaphragm. The potential difference is proportional 
to the pressure, and also depends on the nature of the diaphragm 
and on the liquid. 

Current, Direct. A current of unvarying direction, as dis- 
tinguished from an alternating current. It may be pulsatory or 
intermittent in character, but must be of constant direction. 

Current, Direct Induced. On breaking a circuit, if it is sus- 
ceptible of exercising self-induction, q. v., an extra current, in 
the direction of the original is induced, which is called "direct" 
because in the same direction as the original. The same is pro- 
duced by a current in one circuit upon a parallel one altogether 
separated from it. (See Induction , Electro-Magnetic — Current, 
Extra,) 

Synonym — Break Induced Current. 

Current, Direction of. The assumed direction of a current is 
from positively charged electrode to negatively charged one ; in a 
galvanic battery from the carbon or copper plate through the 
outer circuit to the zinc plate and back through the electrolyte to 
the carbon or copper plate. (See Current.) 

Current, Displacement. The movement or current of elec- 
tricity taking place in a dielectric during displacement. It is 
theoretical only and can only be assumed to be of infinitely short 
duration. (See Displacement, Electric.) 

Currents, Eddy Displacement. The analogues of Foucault 
currents, hypothetically produced in the mass of a dielectric by 
the separation of the electricity or by its electrification. (See 
Displacement. ) 

Current, Extra. When a circuit is suddenly opened or 
closed a current of very brief duration, in the first case in the same 
direction, in the other case in the opposite direction, is produced, 
which exeeeds the ordinary current in intensity. A high poten- 
tial difference is produced for an instant only. These are called 
extra currents. As they are produced by electro-magnetic induc- 
tion, anything which strengthens the field of force increases the 
potential difference to which they are due. Thus the wire may be 
wound in a coil around an iron core, in which case the extra cur- 
rents may be very strong. (See Induction, Self— Coil, Spark.) 

Current, Faradic. A term in medical electricity for the induced 
or secondary alternating current, produced by comparatively high 
electro-motive force, such as given by an induction coil or 
magneto-generator, as distinguished from the regular battery 
current. 



STANDARD ELECTRICAL DICTIONARY. 163 

Current, Foucault. A current produced in solid conductors, 
and which is converted into heat (Ganot). These currents are 
produced by moving the conductors through a field, or by altering 
the strength of a field in which they are contained. They are the 
source of much loss of energy and other derangement in "dynamos 
and motors, and to avoid them the armature cores are laminated, 
the plane of the laminations being parallel to the lines of force. 
(See Core, Laminated.) 

The presence of Foucault currents, if of long duration, is shown 
by the heating of the metal in which they are produced. In dyna- 
mo armatures they are produced sometimes in the metal of the 
windings, especially if the latter are of large diameter. 

Synonyms — Eddy Currents — Local Currents — Parasitical Cur- 
rents. 

Current, Franklinic. In electro-therapeutics the current pro- 
duced by a frictional electric machine. 

Current, Induced. The current produced in a conductor by 
varying the conditions of a field of force in which it is placed ; a 
current produced by induction. 

Current Induction. Induction by one current on another or 
by a portion of a current on another portion of itself. (See 
Induction,) 

Current Intensity. Current strength, dependent on or defined 
by the quantity of electricity passed by such current in a given 
time. The practical unit of current intensity is the ampere, equal 
to one coulomb of quantity per second of time. 

Current, Inverse Induced. The current induced in a con- 
ductor, when in a parallel conductor or in one having a parallel 
component a current is started, or is increased in strength. It is 
opposite in direction to the inducing current and hence is termed 
inverse. (See Induction , Electro-magnetic.) The parallel conduc- 
tors may be in one circuit or in two separate circuits. 

Synonyms — Make-induced Current — Reverse-induced Current. 

Current, Jacobi's Unit of. A current which will liberate one 
cubic centimeter of mixed gases (hydrogen and oxygen) in a water 
voltameter per minute, the gases being measured at o° C. (32 F. 
and 760 mm. (29.92 inches) barometric pressure. It is equal to 
.0961 ampere. 

Current, Joint. The current given by several sources acting 
together. Properly, it should be restricted to sources connected in 
series, thus if two battery cells are connected in series the current 
they maintain is their joint current. 



164 STANDARD ELECTRICAL DICTIONARY. 

Current, Linear. A current passing through a straight con- 
ductor ; a current whose path follows a straight line. 

Current, Make and Break. A succession of currents of short 
duration, separated by absolute cessation of current. Such a 
current is produced by a telegraph key, or by a microphone badly 
adjusted, so that the circuit is broken at intervals. The U. S. 
Courts have virtually decided that the telephone operates by the 
uudulatory currents, and not by a make and break current. Many 
attempts have been made to produce a telephone operating by a 
demonstrable make and break current, on account of the above 
distinction, in hopes of producing a telephone outside of the scope 
of the Bell telephone patent. 

Current=meter. An apparatus for indicating the strength of a 
current. (See Ammeter.) 

Current, Negative. In the single needle telegraph system the 
current which deflects the needle to the left. 

Current, Nerve and Muscle. A current of electricity yielded by 
nerves or muscles. Under proper conditions feeble currents can be 
taken from nerves, as the same can be taken from muscles. 

Current, Opposed. The current given by two or more sources 
connected in opposition to each other. Thus a two volt and a one 
volt battery may be connected in opposition, giving a net voltage 
of only one volt, and a current due to such net voltage. 

Current, Partial. A divided or branch current. A current 
which goes through a single conductor to a point where one or 
more other conductors join it in parallel, and then divides itself 
between the several conductors, which must join further on, pro- 
duces partial currents. It produces as many partial currents as the 
conductors among which it divides. The point of division is 
termed the point of derivation. 

Synonym — Derived Current. 

Current, Polarizing. In electro-therapeutics, a constant current. 

Current, Positive. In the single needle telegraph system the 
current which deflects the needle to the right. 

Current, Pulsatory. A current of constant direction, but 
whose strength is constantly varying, so that it is a series of pul- 
sations of current instead of a steady flow. 

Current, Rectified. A typical alternating current is repre- 
sented by a sine curve, whose undulations extend above and below 
the zero line. If by a simple two member commutator the cur- 
rents are caused to go in one direction, in place of the sine curve 
a series of short convex curves following one another and all the 



STANDARD ELECTRICAL DICTIONARY. 165 

same side of the zero line results. The currents all in the same 
direction, become what is known as a pulsating current. 
Synonym — Redressed Current. 

Current, Rectilinear. A current flowing through a rectilinear 
conductor. The action of currents depending on their distance 
from the points where they act, their contour is a controlling factor. 
This contour is determined by the conductors through which they 
flow. 

Current Reverser. A switch or other contrivance for reversing 
the direction of a current in a conductor. 

Currents, Amperian. The currents of electricity assumed by 
Ampere's theory to circulate around a magnet. As they repre- 
sent the maintenance of a current or of currents without the 
expenditure of energy ^they are often assumed to be of molecular 
dimensions. As they all go in the same sense of rotation and are 
parallel to each other the result is the same as if a single set of 
currents circulated around the body of the magnet. More will 
be found on this subject under Magnetism. The Amperian cur- 
rents are purely hypothetical and are predicated on the existence of 
a field of force about a permanent magnet. (See Magnetism , 
Ampere } s Theory of .) 




..^ 



Figs. 118-119. Direction of Amperian Currents. 

If the observer faces the north pole of a magnet the Amperian 
currents are assumed to go in the direction opposite to that of a 
watch, and the reverse for the south pole. 

Currents, Angular. Currents passing through conductors 
which form an angle with each other. 

Currents, Angular, Laws of. 1. Two rectilinear currents, 
the directions of which form an angle with each other, attract one 
another when both approach to or recede from the apex of the 
angle. 

2. They repel one another, if one approaches and the other 
recedes from the apex of the angle. 



166 STANDARD BlvKCTRICAIv DICTIONARY. 

Currents, Earth. In long telegraph lines having terminal 
grounds or connected to earth only at their ends, potential differ- 
ences are sometimes observed that are sufficient to interfere with 
their working and which, of course, can produce currents. These 
are termed earth-currents. It will be noted that they exist in the 
wire, not in the earth. They may be of 40 milliamperes strength, 
quite enough to work a telegraph line without any battery. Iyines 
running N. B. and S. W. are most affected ; those running N. W. 
and S. B. very much less so. These currents only exist in lines 
grounded at both ends, and appear in underground wires. Hence 
they are not attributable to atmospheric electricity. According to 
Wilde they are the primary cause of magnetic storms ', q. v. , but 
not of the periodical changes in the magnetic elements. (See 
Magnetic Elements.) 

Synonym, — Natural Currents. 

Current, Secondary, (a) A current induced in one conductor 
by a variation in the current in a neighboring one ; the current 
produced in the secondary circuit of an induction coil or alternating 
current converter. 

(b) The current given by a secondary battery. This terminology 
is not to be recommended. 

Current, Secretion. In electro-therapeutics, a current due to 
stimulation of the secretory nerves. 

Current Sheet, {a) If two terminals of an active circuit are 
connected to two points of a thin metallic plate the current spreads 
over or occupies practically a considerable area of such plate, and 
this portion of the current is a current sheet. 

The general contour of the current sheet can be laid out in lines of 
flux. Such lines resemble lines of force. Iyike the latter, they are 
purely an assumption, as the current is not in any sense composed 
of lines. 

(b) A condition of current theoretically brought about by the 
Amperian currents in a magnet. Bach molecule having, its own 
current, the contiguous portions of the molecules counteract each 
other and give a resultant zero current. All that remains is the 
outer sheet of electric current that surrounds the whole. 

Current, Sinuous. A current passing through a sinuous con- 
ductor. 

Currents, Multiphase. A term applied to groups of currents 
of alternating type which constantly differ from each other by a 
constant proportion of periods of alternation. They are produced 
on a single dynamo, the winding being so contrived that two, 
three or more currents differing a constant amount in phase are 



STANDARD ELECTRICAL DICTIONARY. 167 

collected from corresponding contact rings. There are virtually as 
many windings on the armature as there are currents to be produced. 
Separate conductors for the currents must be used throughout. 
Synonyms — Polyphase Currents — Rotatory Currents. 

Currents of Motion. In electro-therapeutics, the currents pro- 
duced in living muscle or nerves after sudden contraction or relax- 
ation. 

Currents of Rest. In electro- therapeutics, the currents travers- 
ing muscular or nervous tissue when at rest. Their existence is 
disputed. 

Currents, Orders of. An intermittent current passing through 
a conductor will induce secondary alternating currents in a closed 
circuit near it. This secondary current will induce a tertiary cur- 
rent in a third closed circuit near it, and so on. The induced 
currents are termed as of the first, second, third and other orders. 
The experiment.is carried out by Henry's coils. (See Cotls, Henry's.) 

Currents, Thermo=electric. These currents, as produced from 
existing thermo-electric batteries, are generated by low potential, 
and are of great constancy. The opposite junctions of the plates 
can be kept at constant temperatures, as by melting ice and con- 
densing steam, so that an identical current can be reproduced at 
will from a thermopile. 

Thermo-electric currents were used by Ohm in establishing his 
law. (Set Ohm's Law.) 

Current, Swelling. In electro-therapeutics, a current gradually 
increasing in strength. 

Current, Undulatory. A current varying in strength without 
any abrupt transition from action to inaction, as in the make and 
break current. The current may be continually changing in 
direction (see Current, Alternating), and hence, of necessity, may 
pass through stages of zero intensity, but such transition must be 
by a graduation, not by an abrupt transition. Such current may 
be represented by a curve, such as the curve of sines. It is 
evident that the current may pass through the zero point as it 
crosses the line or changes direction without being a make and 
break current. When such a current does alternate in direction it 
is sometimes called a ' ' shuttle current. ' ' The ordinary commercial 
telephone current and the alternating current is of this type. (See 
Current, Make and Break.) 

Current, Unit. Unit current is one which in a wire of unit length, 
bent so as to form an arc of a circle of unit length of radius, would 
act upon a unit pole (see Magnetic Pole, Unit,) at the center of the 



168 STANDARD ELECTRICAL DICTIONARY. 

circle with unit force. Unit length is the centimeter ; unit force 
is the dyne. 

Current, Wattless, Whenever there is a great difference in 
phase in an alternating current dynamo between volts and current, 
the true watts are much less than the product of the virtual volts 
and amperes, because the true watts are obtained by multiplying 
the product of the virtual volts and amperes by the cosine of the 
angle of lag (or lead). Any alternating current maybe resolved 
into two components in quadrature with each other, one in phase 
with the volts, the other in quadrature therewith, the former is 
termed by S. P. Thompson the Working Current, the latter the 
Wattless Current. The greater the angle of lag the greater will be 
the wattless current. 

Curve, Arrival. A curve representing the rate of rise of intensity 
of current at the end of a long conductor when the circuit has been 
closed at the other end. In the Atlantic cable, for instance, it would 
require about 108 seconds for the current at the distant end to attain 
9-10 of its full value. The curve is drawn with its abscissas repre- 
senting time and its ordinates current strength. 

Curve, Characteristic. A curve indicating, graphically, the rela- 
tions between any two factors, which are interdependent, or which 
vary simultaneously. Thus in a dynamo, the voltage increases 
with the speed of rotation, and a characteristic curve may be based 
on the relations between the speed of rotation and voltage devel- 
oped. The current produced by a dynamo varies with the electro- 
motive force, and a curve can express the relations between the 
electro-motive force and the current produced. 

A characteristic curve is usually laid out by rectangular co-ordi- 
nates (see Co-ordinates). Two lines are drawn at right angles to 
each other, one vertical, and the other horizontal. One set of data 
are marked off on the horizontal line, say one ampere, two amperes, 
and so on, in the case of a dynamo's characteristic curve. 

For each amperage of current there is a corresponding voltage 
in the circuit. Therefore on each ampere mark a vertical is 
erected, and on that the voltage corresponding to such amperage is 
laid off. This gives a series of points, and these points may be 
connected by a curve. Such curve will be a characteristic curve. 

The more usual way of laying out a curve is to work directly 
upon the two axes. On one is laid off the series of values of 
one set of data ; on the other the corresponding series of values 
of the other dependent data. Vertical lines or ordinates, q. v., are 
erected on the horizontal line or axis of abscissas at the points 
laid off; horizontal lines or abscissas, q. v., are drawn from the 



STANDARD ELECTRICAL DICTIONARY. 



169 



points laid off on the vertical line or axis of ordinates. The char- 
acteristic curve is determined by the intersections of each corre- 
sponding pair of abscissa and ordinate. 

Variations exist in characteristic curve methods. Thus to get 
the characteristic of a commutator, radial lines may be drawn 
from a circle representing its perimeter. Such lines may be of length 
proportional to the voltage developed on the commutator at the 
points whence the lines start. A cut giving an example of such a 
curve is given in Fig. 125. (See Curve of Distribution of Potential 
in Armature.) 

There is nothing absolute in the use of ordinates or abscissas. 
They may be interchanged. Ordinarily voltages are laid off as ordi- 
nates, but the practise may be reversed. The same liberty holds 
good for all characteristic curves. Custom, however, should be 
followed. 

Synonym — Characteristic. 



100 

80 
JO 










F*L 


I\£ 










\ 








► «> 
** 






K / 








i 










\ 




\S 


-s- 




N 


50 

-.« 

O *o 

> 




/m 


\ 




% 


fa 


V 


N 














X 


> 






% 








\ 


*** 






T v - 






"«%, 




*'•• 


10 










***-. 






""" 



















10 20 30 40 .50 60 70 60 

AMPER ES. 
Fig. 120. Characteristic Curve of a Dynamo with Horse Power Curves. 

Curve, Characteristic, of Converter. The characteristic curve 
of the secondary circuit of an alternating current converter. It 
gives by the usual methods (see Curve, Characteristic ,) the rela- 
tions between the electro-motive force and the current in the 
secondary circuit at a fixed resistance. If connected in parallel a 
constant electro-motive force is maintained, and the curve is virtu- 
ally a straight line. If connected in series an elliptical curve is 
produced. 



170 



STANDARD ELECTRICAL DICTIONARY. 



Curve, Charging. In secondary battery manipulation, a curve 
indicating the increase of voltage as the charging is prolonged. 
The rise in voltage with the duration of the charging current is 
not uniform. In one case, shown in the cut, there was a brief rapid 
rise of about o. i volt ; then a long slow rise for o. 15 volt ; then a 
more rapid rise for nearly 0.40 volt, and then the curve became 
a horizontal line indicating a cessation of increase of voltage. The 
charging rate should be constant. 



C.50 
£.4 5 

♦*-*° 
2.35 

ft. 20 
*-!» 
CIO 

A -05 



j 






























1 










mm i 


= 










































: 


: 










































: 


: 










































: 


; 










































: 


[ 










































z 


: 






























r 














: 










































E 


3 










































r 


= 












































^\ 


09 






































HOURS q 



i 5 * 4 . ' *5> 6 . - 7 8 < 9 * IQ Jl 12 15. 14 J5 16 17 19 . 19 20 21 22 



Fig. i2i. Charging Curve of a Secondary Battery. 

The horizontal line is laid off in hours, the vertical in volts, so 
that the time is represented by abscissas and the voltage by ordi- 
nates of the curve. 

Curve, Discharging. A characteristic curve of a storage bat- 
tery, indicating the fall in voltage with hours of discharge. The 
volts may be laid off on the axis of ordinates, and the hours of 
discharging on the axis of abscissas. To give it meaning the rate of 
discharge must be constant. 

Curve, Electro=motive Force. A characteristic curve of a 
dynamo. It expresses the relation between its entire electro- 
motive force, as calculated by Ohm's Law, and the current inten- 
sities corresponding thereto. To obtain the data the dynamo is 
driven with different resistances in the external circuit and the current 
is measured for each resistance. This gives the amperes. The total 
resistance of the circuit, including that of the dynamo, is known. 
By Ohm's Law the electro-motive force in volts is obtained for 
each case by multiplying the total resistance of the circuit in 
ohms by the amperes of current forced through such resistance. 
Taking the voltages thus calculated for ordinates and the corre- 
sponding amperages for abscissas the curve is plotted. An 
example is shown in the cut. 



STANDARD ELECTRICAL DICTIONARY. 



171 



Curve, External Characteristic. A characteristic curve of 
a dynamo, corresponding to the electro-motive force curve, except 
that the ordinates represent the voltages of the external circuit, 
the voltages as taken directly from the terminals of the machine, 



r 



O 30 
> 



E "" '^ j 8 

C^ *^_ |__ 

f -/ f . ! ! 

/ i §!__ • 

T I'l l i-i 1 i 

ol k . :f 



20 30 40 

AMPERES, 



*» «£ 



Fig. 122. Characteristic Curve op A Dynamo. 

instead of the total electro-motive force of the circuit. The dyna- 
mo is run at constant speed. The resistance of the external circuit 
is varied. The voltages at the terminals of the machine and the 
amperages of current corresponding thereto are determined. Using 
the voltages thus determined as ordinates and the corresponding 
amperages as abscissas the external characteristic curve is plotted. 

This curve can be mechanically produced. A pencil may be 
moved against a constant force by two electro-magnets pulling at 
right angles to each other. One must be excited by the main cur- 
rent of the machine, the other by a shunt current from the terminals 
of the machine. The point of the pencil will describe the curve. 

Curve, Horse Power. Curves indicating electric horse power. 
They are laid out with co-ordinates, volts being laid off on the axis 
of ordinates, and amperes on the axis of abscissas generally. The 
curves are drawn through points where the product of amperes by 
volts equals 746. On the same diagram 1, 2, 3 . . . . and any other 
horse powers can be plotted if within the limits. See Fig. 120. 

Curve, Isochasmen. A line drawn on the map of the earth's 
surface indicating the locus of equal frequency of auroras. 

Curve, Life. A characteristic curve showing the relations 
between the durability and conditions affecting the same in any 



172 



STANDARD ELECTRICAL DICTIONARY. 



appliance. It is used most for incandescent lamps. The hours of 
burning before failure give ordinates, and the rates of burning, ex- 
pressed indirectly in volts or in candle-power, give abscissas. For 
each voltage or for each candle-power an average duration is 
deducible from experience, so that two dependent sets of data are 
obtained for the construction of the curve. 

Curve, Load. A characteristic curve of a dynamo, expressing 
the relation between its voltage and the amount of excitation under 















Fig 


287. 














CO 

5 


























o 

> 












C 2 


jr— - 




— — i; 


—100 







































bo 














































































/ 


























// 


w 
























MOO/ 
150' 


7 
















AMPE 


RE-TI 


JRNS. 



10,000 



Fig. 123. Load Curves. 

a definite condition of ampere load, at a constant speed. The 
ordinates represent voltage, the abscissas ampere turns in the field, 
and the curves may be constructed for a flow of o, 50, 100, or. . , or 
any other number of amperes. 

Curve, Magnetization. A characteristic curve of an electro- 
magnet, indicating the relation of magnetization to exciting cur- 
rent. Laying off on the axis of ordinates the quantities of magnet- 
ism evoked, and the corresponding strengths of the exciting current 
on the axis of abscissas, the curve can be plotted. It first rises 
rapidly, indicating a rapid increase of magnetization, but grows 
nearly horizontal as the iron becomes more saturated. The effect 
due to the coils alone, or the effect produced in the absence of iron 
is a straight line, because air does not change in permeability. 

Curve of Distribution of Potential in Armature. A charac- 
teristic curve indicating the distribution of potential difference 
between adjoining sections of the commutator of an armature in 
different positions all around it. The potential differences are 
taken by a volt-meter or potential galvanometer, connection with 



STANDARD ELECTRICAL DICTIONARY. 



173 



the armature being made by two small metal brashes, held at a 
distance apart equal to the distance from centre to centre of two 
adjoining commutator bars. The curve is laid out as if by polar 
co-ordinates extending around the cross-section of the commutator, 

































-A 

-c 






•'' 






















</ 




























*•/ i 




























$// 




























i 














r o\ 


.S.J 


\.o 


*5- 








.& 


1 






ef 


, tC 


. p\ 


i, 

■ 














-I. 








STRENGTH OF EXCITING CURRENT. 

Fig. 124. Magnetization Curve. 

with the distances from the commutator surface to the curve pro- 
portional to the potential differences as determined- by shifting the 
pair of brushes all around the commutator. 

The above is S. P. Thompson's method. Another method of W. 
M. Mordey involves the use of a pilot brush. (See Brush, Pilot.) 
Otherwise the method is in general terms identical with the above. 




Fig. 125. Armature Curve. Fig. 126. Development of Armature Curve. 

Curve of Dynamo. The characteristic curve of a dynamo. (See 
Curve, Characteristic.) 

Curve of Sines. An undulating curve representing wave mo- 
tion. It is produced by compounding a simple harmonic motion, 
or a two and fro motion like that of an infinitely long pendulum 
with a rectilinear motion. Along a horizontal line points may be 
laid off to represent equal periods of time. Then on each point a 



174 



STANDARD ELECTRICAL DICTIONARY. 




perpendicular must be erected. The length of each must be equal 
to the length of path traversed by the point up to the expiration of 
each one of the given intervals of time. The abscissas are propor- 
tional to the times and the ordinates to the sines of angles propor- 
tional to the times. Thus if a circle be drawn upon the line 
and divided into thirty-two parts of equal angular value, the sines 
of these angles may be taken as the ordinates and the absolute 
distance or length of arc of the angle will give the abscissas. 

Synonyms — Sine Curve — Sinusoidal Curve — Harmonic Curve. 



270° 360° 



Fig. 127. Curve of Sines. 

Curve of Saturation of the Magnetic Circuit. A characteristic 
curve whose ordinates may represent the number of magnetic lines 
of force induced in a magnetic circuit, and whose abscissas may 
represent the ampere turns of excitation or other representative of 
the inducing force. 

Curve of Torque. A characteristic curve showing the relations 
between torque, q. v., and current in a dynamo or motor. 

Curve, Permeability Temperature. A characteristic curve 
expressing the changes in permeability of a paramagnetic sub- 
stance as the temperature changes. The degrees of temperature 
may be abscissas, and the permeabilities corresponding thereto 
ordinates of the curve. 

Cut In. v. To connect any electric appliance, mechanism or 
conductor, into a circuit. 

Cut Out. v. The reverse of to cut in ; to remove from a circuit 
any conducting device, and sometimes so arranged as to leave the 
circuit completed in some other way. 

Cut Out. An appliance for removing any apparatus from an 
electric circuit, so that no more current shall pass through such 
apparatus, and sometimes providing means for closing the circuit 
so as to leave it complete after the removal of the apparatus. 



STANDARD ELECTRICAL DICTIONARY. 175 

Cut Out, Automatic, (a) A mechanism for automatically 
shunting an arc or other lamp when it ceases to work properly. It 
is generally worked by an electro-magnet of high resistance placed 
in parallel with the arc. If the arc grows too long the magnet 
attracts its armature, thereby completing a shunt of approximately 
the resistance of the arc, and which replaces it until the carbons 
approach again to within a proper distance. Sometimes a strip or 
wire of fusible metal is arranged in shunt with the arc. When the 
arc lengthens the current through the wire increases, melts it and 
a spring is released which acts to complete or close a shunt circuit 
of approximately arc-resistance. 

(b) See Safety Device — Safety Fuse. 

(c) See below. 

Cut=out, Magnetic. A magnetic cut-out is essentially a coil of 
wire with attracted core or armature. When the coil is not excited 
the core, by pressing down a strip of metal or by some analogous 
arrangement, completes the circuit. When the current exceeds a 
certain strength the core rises as it is attracted and the circuit is 
opened. 

Cut=out, Safety. A block of porcelain or other base carrying a 
safety fuse, which melts and breaks the circuit before the wire 
connected to it is dangerously heated. 

Synonyms — Fuse Block — Safety Catch — Safety Fuse. 

Cut Out, Wedge. A cut out operated by a wedge. The line ter- 
minals consist of a spring bearing against a plate, the circuit being 
completed through their point of contact. A plug or wedge com- 
posed of two metallic faces insulated from each other is adapted to 
wedge the contact open. Terminals of a loop circuit are connected 
to the faces of the w r edge. Thus on sliding it into place, the loop 
circuit is brought into series in the main circuit. 

Synonym — Plug Cut Out — Spring Jack. 

Cutting of Lines of Force. A field of force is pictured as made 
up of lines of force ; a conductor swept through the field is pictured 
as cutting these lines. By so doing it produces potential difference 
or electro-motive force in itself with a current, if the conductor is 
part of a closed circuit. 

Cycle of Alternation. A full period of alternation of an alter- 
nating current. It begins properly at the zero line, goes to a max- 
imum value in one sense and returns to zero, goes to maximum 
in the other sense and returns to zero. 

Cystoscopy. Examination of the human bladder by the introduc- 
tion of a special incandescent electric lamp. The method is due 
to Hitze. 



176 STANDARD ELECTRICAL DICTIONARY. 

Damper, (a) A copper frame on which the wire in a galvan- 
ometer is sometimes coiled, which acts to damp the oscillations of 
the needle. 

(6) A tube of brass or copper placed between the primary and 
secondary coils of an induction coil. It cuts off induction and 
diminishes the current and potential of the secondary circuit. On 
pulling it out, the latter increases. It is used on medical coils to 
adjust their strength of action. 

Damping. Preventing the indicator of an instrument from 
oscillating in virtue of its own inertia or elasticity. In a galvan- 
ometer it is defined as resistance to quick vibrations of the needle, 
in consequence of which it is rapidly brought to rest when deflected 
(Ayr ton). In dead-beat galvanometers (see Galvanometer ', Dead- 
Beat,) damping is desirable in order to bring the needle to rest 
quickly ; in ballistic galvanometers (see Galvanometer, Ballistic,) 
damping is avoided in order to maintain the principle of the instru- 
ment. Damping may be mechanical, the frictional resistance of 
air to an air- vane, or of a liquid to an immersed diaphragm or 
loosely fitting piston, being employed. A dash-pot, q. v., is an 
example of the latter. It may be electro-magnetic. A mass of 
metal near a swinging magnetic needle tends by induced currents 
to arrest the oscillations thereof, and is used for this purpose in 
dead-beat galvanometers. This is termed, sometimes, magnetic 
friction. The essence of damping is to develop resistance to move- 
ment in some ratio proportional to velocity, so that no resistance 
is offered to the indicator slowly taking its true position. (See 
Galvanometer, Dead-Beat.) 

Dash=Pot. A cylinder and piston, the latter loosely fitting or 
perforated, or some equivalent means being provided to permit 
movement. The cylinder may contain a liquid such as glycerine, 
or air only. Thus the piston is perfectly free to move, but any 
oscillations are damped (see Damping). In some arc lamps the 
carbon holder is connected to a dash-pot to check too sudden move- 
ments of the carbon. The attachment may be either to the piston 
or to the cylinder. In the Brush lamp the top of the carbon holder 
forms a cylinder containing glycerine, and in it a loosely fitting 
piston works. This acts as a dash-pot. 

Dead Beat. adj. Reaching its reading quickly ; applied to 
instruments having a moving indicator, which normally would 
oscillate back and forth a number of times before reaching its 
reading were it not prevented by damping. (See Galvanometer ', 
Aperiodic — Damping.) 

Dead Earth. A fault in a telegraph line which consists in the 
wire being thoroughly grounded or connected to the earth. 



STANDARD ELECTRICAL DICTIONARY. 177 

Dead Point of an Alternator. A two-phase alternator of the 
ordinary type connected as a motor to another alternator cannot 
start itself, as it has dead points where the relations and polarity of 
field and armature are such that there is no torque or turning 
power. 

Dead=Turns. In the winding of an armature, a given percentage 
of the turns, it may be 80 per cent., more or less, is assumed to be 
active ; the other 20 per cent, or thereabouts, is called dead-turns. 
This portion represents the wire on such portions of the armature 
as comes virtually outside of the magnetic field. They are termed 
dead, as not concurring to the production of electro-motive force. 

Dead Wire, (a) The percentage or portion of wire on a dynamo 
or motor armature that does not concur in the production of electro- 
motive force. The dead-turns, q. v., of a drum armature or the 
inside wire in a Gramme ring armature are dead wire. 

(b) A disused and abandoned electric conductor, such as a tele- 
graph wire. 

(c) A wire in use, but through which, at the time of speaking, 
no current is passing. 

Death, Electrical. Death resulting from electricity discharged 
through the animal system. The exact conditions requisite for 
fatal results have not been determined. High electro-motive force 
is absolutely essential ; a changing current, pulsatory or alternating, 
is most fatal, possibly because of the high electro-motive force of a 
portion of each period. Amperage probably has something to do 
with it, although the total quantity in coulombs may be very small. 
As applied to the execution of criminals, the victim is seated in a 
chair and strapped thereto. One electrode with wet padded surface 
is placed against his head or some adjacent part. Another electrode 
is placed against some of the lower parts, and a current from an 
alternating dynamo passed for 15 seconds or more. The potential 
difference of the electrodes is given at 1,500 to 2,000 volts, but of 
course the maximum may be two or three times the measured 
amount, owing to the character of the current. 

Decalescence. The converse of recalescence, q. v. When a 
mass of steel is being heated as it reaches the temperature of recal- 
escense it suddenly absorbs a large amount of heat, apparently 
growing cooler. 

Deci. Prefix originally used in the metric system to signify one- 
tenth of, now extended to general scientific units. Thus deci- 
meter means one-tenth of a meter ; decigram, one-tenth of a gram. 

Declination, Angle of. The angle intercepted between the 
true meridian and the axis of a magnetic needle at any place. The 



178 STANDARD KlvKCTRICAI. DICTIONARY. 

angle is measured to east or west, starting from the true meridian 
as zero. 

Declination of the Magnetic Needle. The deviation of the 
magnetic needle from the plane of the earth's meridian. It is also 
called the variation of the compass. (See Magnetic Elements.} 

Decomposition. The reduction of a compound substance into 
its constituents, as in chemical analysis. The constituents may 
themselves be compounds or proximate constituents, or may be 
elemental or ultimate constituents. 

Decomposition, Electrolytic. The decomposition or separa- 
tion of a compound liquid into its constituents by electrolysis. 
The liquid must be an electrolyte , q. v., and the decomposition 
proceeds subject to the laws of electrolysis, q. v. See also Electro- 
lytic Analysis. 

Decrement. When a suspension needle which has been dis- 
turbed is oscillating the swings gradually decrease in amplitude if 
there is any damping, as there always is. The decrement is the 
ratio of the amplitude of one oscillation to the succeeding one. 
This ratio is the same for any successive swings. 

De=energize. To cut off its supply of electric energy from an 
electric motor, or any device absorbing and worked by electric 
energy. 

Deflagration. The explosive or violent volatilizing and dissi- 
pating of a substance by heat, violent oxidation and similar means. 
It may be applied among other things to the destroying of a con- 
ductor by an intense current, or the volatilization of any material 
by the electric arc. 

Deflecting Field. The field produced in a galvanometer by the 
current which is being tested, and which field deflects the needle, 
such deflection being the measure of the current strength. 

Deflection. In magnetism the movement out of the plane of 
the magnetic meridian of a magnetic needle, due to disturbance 
by or attraction towards a mass of iron or another magnet. 

Deflection Method. The method of electrical measurements in 
which the deflection of the index of the measuring instrument is 
used as the measure of the current or other element under examin- 
ation. It is the opposite of and is to be distinguished from the zero 
or null method, q. v. In the latter conditions are established 
which make the index point to zero and from the conditions neces- 
sary for this the measurement is deduced. The Wheatstone 
Bridge, q. v., illustrates a zero method, the sine or the tangent 
compass, illustrates a deflection method. The use of deflec- 



STANDARD ELECTRICAL DICTIONARY. 179 

tion methods involves calibration, q. v., and the commercial 
measuring instruments, such as ammeters and volt meters, which 
are frequently calibrated galvanometers, are also examples of deflec- 
tion instruments. 

Degeneration, Reaction of. The diminished sensibility to electro- 
therapeutic treatment exhibited by the human system with con- 
tinuance of the treatment in question. The general lines of 
variation are stated in works on the subject. 

Deka. Prefix originally used in the metric system to signify 
multiplying by ten, as dekameter, ten meters, dekagram, ten 
grams ; now extended to many scientific terms. 

De la Rive's Floating Battery. A small galvanic couple, 
immersed in a little floating cell and connected through a coil of 
wire immediately above them. When the exciting battery solution 
is placed in the cell the whole, as it floats in a larger vessel, 
turns until the coil lies at right angles to the magnetic needle. 
Sometimes the two plates are thrust through a cork and floated thus 
in a vessel of dilute sulphuric acid. 

A magnet acts to attract or repel the coil in obedience to 
Ampere's Theory, (See Magnetism, Ampere's Theory of.) 

Delaurier's Solution. A solution for batteries of the Bunsen 
and Grenet type. It is of the following composition : 

Water, 2,000 parts ; potassium bichromate, 184 parts ; sulphuric 
acid, 428 parts. 

Demagnetization. Removal of magnetism from a paramag- 
netic substance. It is principally used for watches which have 
become magnetized by exposure to the magnetic field surround- 
ing dynamos or motors. 

The general principles of most methods are to rotate the object, 
as a watch, in a strong field, and while it is rotating to gradually 
remove it from the field, or to gradually reduce the intensity of the 
field itself to zero. A conical coil of wire within which the field is 
produced in which the watch is placed is sometimes used, the idea 
being that the field within such a coil is strongest at its base. Such a 
coil supplied by an alternating current is found effectual (J. J. 
Wright). 

If a magnetized watch is made to turn rapidly at the end of a 
twisted string and is gradually brought near to and withdrawn from 
the poles of a powerful dynamo it may be considerably improved. 

A hollow coil of wire connected with a pole changer and dip- 
battery has been used. The battery creates a strong field within 
the coil. The watch is placed there and the pole changer is worked 
30 as to reverse the polarity of the field very frequently. By the 



180 STANDARD ELECTRICAL DICTIONARY. 

same action of the pole changer the plates of the battery are gradu- 
ally withdrawn from the solution so as to gradually reduce the 
magnetic field to zero while constantly reversing its polarity. 
(G.M.Hopkins.) 

Steel may be demagnetized by jarring when held out of the 
magnetic meridian, or by heating to redness. 

Density, Electric Superficial. The relative quantity of elec- 
tricity residing as an electric charge upon a unit area of surface. It 
may be positive or negative. 

Synonyms — Density of Charge — Surface Density. 

Dental Mallet, Electric. A dentist's instrument for hammering 
the fillings as inserted into teeth. It is a little hammer held in a 
suitable handle, and which is made to strike a rapid succession of 
blows by electro-magnetic motor mechanism. 

Depolarization, (a) The removal of permanent magnetism. 

(See Demagnetization.) 

(b) The prevention of the polarization of a galvanic cell. It is 
effected in the Grove battery by the reduction of nitric acid; in the 
Bunsen, by the reduction of chromic acid ; in the Smee battery, 
mechanically, by the platinum coated or rather platinized negative 
plate. Other examples will be found .under the description of 
various cells and batteries. A fluid which depolarizes is termed a 
depolarizer or depolarizing fluid or solution. (See Electropoion 
Fluid.) 

Deposit, Electrolytic. The metal or other substance precip- 
itated by the action of a battery or other current generator. 

Derivation, Point of. A point where a circuit branches or 
divides into two or more leads. The separate branches then 
receive derived or partial currents. 

Desk Push. A press or push button, with small flush rim, for 
setting into the woodwork of a desk. 

Detector. A portable galvanometer, often of simple construction, 
used for rough or approximate work. 

Detector, Lineman's. A portable galvanometer with a high 
and a low resistance actuating coil, constructed for the use of line- 
men and telegraph constructors when in the field, and actually 
putting up, repairing or testing lines. 

Deviation, Quadrantal. Deviation of the compass in iron or 
steel ships due to the magnetization of horizontal beams by the earth's 
induction. The effect of this deviation disappears when the ship 
is in the plane of the electric meridian, or at right angles thereto ; 
its name is taken from the fact that a swing of the ship through a 



STANDARD ELECTRICAL DICTIONARY. 181 

quadrant brings the needle from zero deviation to a maximum and 
back to zero. 

Deviation, Semicircular. Deviation of the compass in iron or 
steel ships due to vertical induction. (See Induction, Vertical.) 
The effect of this induction disappears when the ship is in the elec- 
tric meridian. Its name is derived from the fact that a swing of 
the ship through half the circle brings the needle from zero devi- 
ation to a maximum and back to zero. 

Dextrotorsal. adj. Wound in the direction or sense of a right- 
handed screw ; the reverse oisinistrotorsal, q. v. 



Fig. 128. Dextrotorsal Helix. 

Diacritical, adj. (a) The number of ampere turns, q. v., required 
to bring an iron core to one half its magnetic saturation, q. v., is 
termed the diacritical number. 

(b) The diacritical point of magnetic saturation is proposed by 
Sylvanus P. Thompson as a term for the coefficient of magnetic 
saturation which gives a magnet core one-half its maximum mag- 
netization. 

Diagnosis, Electro. A medical diagnosis of a patient's condi- 
tion based on the action of different parts of the body under electric 
excitement. 

Diamagnetic. adj. Possessing a negative coefficient of magnetic 
susceptibility ; having permeability inferior to that of air. Such 
substances placed between the poles of a magnet are repelled ; if in 
the form of bars, they tend to turn so as to have their long axis at 
right angles to the line joining the poles. The reason is that the 
lines of force always seek the easiest path, and these bodies having 
higher reluctance than air, impede the lines of force, and hence 
are as far as possible pushed out of the way. The above is the 
simplest explanation of a not well understood set of phenomena. 
According to Tyndall, " the diamagnetic force is a polar force, the 
polarity of diamagnetic bodies being opposed to that of paramag- 
netic ones under the same conditions of excitement. ' ' Bismuth is 
the most strongly diamagnetic body known ; phosphorus, anti- 
mony, zinc, and many others are diamagnetic. (See Paramag- 
netic.) 

Diagometer. An apparatus for use in chemical analysis for 
testing the purity of substances by the time required for a charged 



182 STANDARD ELECTRICAL DICTIONARY. 

surface to be discharged through them to earth. It is the invention 
of Rousseau. 

An electrometer is charged with a dry pile. One of its terminals 
is connected with one surface of the solution or substance to be 
tested, and the other with the other surface. The time of discharge 
gives the index of the purity of the substance. 

Diamagnetic Polarity. Treating diamagnetism as due to a 
polar force, the polarity of a diamagnetic body is the reverse of the 
polarity of iron or other paramagnetic bodies. A bar-shaped dia- 
magnetic body in a field of force tends to place itself at right angles 
to the lines of force. 

Diamagnetism. (a) The science or study of diamagnetic sub- 
stances and phenomena. 

(b) The magnetic property of a diamagnetic substance. 

Diameter, of Commutation. The points on the commutator 
of a closed circuit ring — or drum — armature, which the brushes 
touch, and whence they take the current, mark the extremities of 
the diameter of commutation. Were it not for the lag this would 
be the diameter at right angles to the line connecting the centers 
of the opposite faces of the field. It is always a little to one side 
of this position, being displaced in the direction of rotation. In 
open circuit armatures the brushes are placed on the diameter at 
right angles to this one, and sometimes the term diameter of com- 
mutation is applied to it. All that has been said is on the supposi- 
tion that the armature divisions correspond not only in connection 
but in position with those of the armature coils. Of course, the 
commutator could be twisted so as to bring the diameter of com- 
mutation into any position desired. 

Diapason, Electric. A tuning-fork or diapason kept in vibra- 
tion by electricity. In general principle the ends of the fork act 
as armatures for an electro-magnet, and in their motion by a mer- 
cury cup or other form of contact they make and break the circuit 
as they vibrate. Thus the magnet alternately attracts and releases 
the leg, in exact harmony with its natural period of vibration. 

Diaphragm, {a) In telephones and microphones a disc of iron 
thrown into motion by sound waves or by electric impulses, accord- 
ing to whether it acts as the diaphragm of a transmitter or receiver. 
It is generally a plate of japanned iron such as used in making 
ferrotype photographs. (See Telephone and Microphone.) 

(b) A porous diaphragm is often used in electric decomposition 
cells and in batteries. The porous cup represents the latter use. 

Dielectric. A non-conductor ; a substance, the different parts 
of which may, after an electric disturbance, remain, without any 



STANDARD ELECTRICAL DICTIONARY. 183 

process of readjustment, and for an indefinite period of time, at 
potentials differing to any extent (Daniell). There is no perfect 
dielectric. The term dielectric is generally only used when an 
insulator acts to permit induction to take place through it, like the 
glass of a Leyden jar. 

Dielectric Constant. The number or coefficient expressing 
the relative dielectric capacity of a medium or substance. (See 
Capacity, Specific Inductive.) 

Dielectric, Energy of. In a condenser, the conducting coat- 
ings are merely to conduct the current all over the surface they 
cover ; the keeping the electricities separated is the work of the 
dielectric, and represents potential energy which appears in the 
discharge. The amount of energy is proportional to the charge, 
and to the potential difference. As any electrified body implies an 
opposite electrification somewhere, and a separating dielectric, the 
existence of a condenser is always implied. 

Dielectric Polarization. A term due to Faraday. It expresses 
what he conceived to be the condition of a dielectric when its 
opposite faces are oppositely electrified. The molecules are sup- 
posed to be arranged by the electrification in a series of polar 
chains, possibly being originally in themselves seats of opposite 
polarities, or having such imparted to them by the electricities. 
The action is analogous to that of a magnet pole on a mass of soft 
iron, or on a pile of iron filings. 

Dielectric Strain. The strain a solid dielectric is subjected to, 
when its opposite surfaces are electrified. A Leyden jar dilates 
under the strain, and when discharged gives a dull sound. The 
original condition is not immediately recovered. Jarring, shaking, 
etc., assist the recovery from strain. The cause of the strain is 
termed Electric Stress. (See Stress, Electric.) This is identical 
with the phenomenon of residual charge. (See Charge, Residual.) 
Each loss of charge is accompanied with a proportional return of 
the dielectric towards its normal condition. 

Dielectric Resistance. The mechanical resistance a body offers 
to perforation or destruction by the electric discharge. 

Dielectric Strength. The resistance to the disruptive discharge 
and depending on its mechanical resistance largely or entirely. It is 
expressible in volts per centimeter thickness. Dry air requires 
40,000 volts per centimeter for a discharge. 

Differential Winding Working. A method of working an elec- 
tro-magnet intermittently, so as to avoid sparking. The magnet 
is wound with two coils. One is connected straight into the cir- 
cuit, the other is connected in parallel therewith with a switch 



184 STANDARD ELECTRICAL DICTIONARY. 

inserted. The coils are so connected that when the switch is 
closed the two are in opposition, the current going through them 
in opposite senses. Thus one overcomes the effect of the other and 
the magnet core shows no magnetism, provided the two coils are 
of equal resistance and equal number of convolutions or turns. 



Fig. 129. Differential Winding Working of Electro-magnetic Apparatus. 

Diffusion. A term properly applied to the varying current 
density found in conductors of unequal cross sectional area. In 
electro-therapeutics it is applied to the distribution of current as it 
passes through the human body. Its density per cross-sectional 
area varies with the area and with the other factors. 

Diffusion Creep. When electrodes of an active circuit are im- 
mersed in a solution of an electrolyte, a current passes electrolytic- 
ally if there is a sufficient potential difference. The current passes 
through all parts of the solution, spreading out of the direct prism 
connecting or defined by the electrodes. To this portion of the 
current the above term is applied. If the electrodes are small 
enough in proportion to the distance between them the current 
transmission or creep outside of the line becomes the principal 
conveyor of the current so that the resistance remains the same 
for all distances. 

Dimensions and Theory of Dimensions. The expression of 
the unitary value of a physical quantity in one or more of the units 
of length (Iy) , time (T) and mass (M) is termed the dimensions of 
such quantity. Thus the dimension or dimensions of a distance is 
simply L, ; of an angle, expressible by dividing the arc by the radius 
is L,-T-Iy or L/L ; of a velocity, expressible by distance divided by 
time — Iy/T ; of acceleration, which is velocity acquired in a unit 
of time, and is therefore expressible by velocity divided by time — 
Iy-i-T/T or Iy/T 2 ; of momentum, which is the product of mass into 
velocity — M Iy/T ; of kinetic energy taken as the product of mass 
into the square of velocity — M L, 2 /T 2 ; of potential energy taken as 
the product of mass into acceleration into space — M X L/T 2 X h 
reducing to ML, 2 /T 2 . The theory is based on three fundamental 
units and embraces all electric quantities. The simple units 



STANDARD ELECTRICAL DICTIONARY. 185 

generally taken are the gram, centimeter and second and the 
dimensions of the fundamental compound units are expressed in 
terms of these three, forming the centimeter-gram-second or 
C. G. S. system of units. Unless otherwise expressed or implied 
the letters L, M and T, may be taken to indicate centimeter, gram 
and second respectively. It is obvious that very complicated 
expressions of dimensions may be built up, and that a mathemat- 
ical expression of unnamed quantities may be arrived at. Dimen- 
sions in their application by these symbols are subject to the laws 
of algebra. They were invented by Fourier and were brought into 
prominence by J. Clerk Maxwell. Another excellent definition 
reads as follows : "By the dimensions of a physical quantity we 
mean the quantities and powers of quantities, involved in the 
measurement of it." (W. T. A. Emtage.) 

Dimmer. An adjustable choking coil used for regulating the 
intensity of electric incandescent lights. Some operate by the 
introduction and withdrawal of an iron core as described for the 
choking coil (see Coil, Choking), others by a damper of copper, 
often a copper ring surrounding the coil and which by moving on 
or off the coil changes the potential of the secondary circuit. 

Dip of Magnetic Needle. The inclination of the magnetic 

needle. (See Elements, Magnetic.) 

Dipping, (a) Acid or other cleaning processes applied by dip- 
ping metals in cleaning or pickling solutions before plating in the 
electroplater's bath. 

(b) Plating by dipping applies to electroplating without a battery 
by simple immersion. Copper is deposited on iron from a solution 
of copper sulphate in this way. 

Synonym — Simple Immersion. 

Dipping Needle. A magnet mounted in horizontal bearings at 
its centre of gravity. Placed in the magnetic meridian it takes the 
direction of the magnetic lines of force of the earth at that point. 
It is acted on by the vertical component of the earth's magnetism, 
as it has no freedom of horizontal movement. (See Mag?ietic 
Elements, and Compass, Inclination.) 

Directing Magnet. In a reflecting galvanometer the magnet 
used for controlling the magnetic needle by establishing a field. It 
is mounted on the spindle of the instrument above the coil and 
needle. 

Synonym — Controlling Magnet. 

Direction, (a) The direction of an electric current is assumed 
to be from a positively charged electrode or terminal to a nega- 
tively charged one in the outer circuit. (See Current.) 



i86 



STANDARD ELECTRICAL DICTIONARY. 



(b) The direction of magnetic and electro-magnetic lines of force 
is assumed to be from north to south pole of a magnet in the outer 
circuit. It is sometimes called the positive direction. 




Fig. 130. Direction of Lines of Force of a Permanent Magnet. 






Fig. 131. Direction of Lines of Force of an Electro-magnet. 
Their general course is shown in the cuts diagrammatically. The 



STANDARD ELECTRICAL DICTIONARY. 187 

circles indicate a compass used in tracing their course. The mag- 
netic needle tends to place itself in the direction of or tangential 
to the lines of force passing nearest it. 

(c) The direction of electrostatic lines of force is assumed to be 
out of a positively charged and to a negatively charged surface. 

Directive Power. In magnetism the power of maintaining itself 
in the plane of the magnetic meridian, possessed by the magnetic 
needle. 

Discharge, Brush. The static discharge of electricity into or 
through the air may be of the brush or spark form. The brush 
indicates the escape of electricity in continuous flow ; the spark 
indicates discontinuity. The conditions necessary to the produc- 
tion of one or the other refer to the nature of the conductor, and 
of other conductors in its vicinity and to the electro-motive force 
or potential difference ; small alterations may transform one into 
the other. The brush resembles a luminous core whose apex touches 
the conductor. It is accompanied by a slight hissing noise. Its 
luminosity is very feeble. The negative conductor gives a smaller 
brush than that of the positive conductor and discharges it more 
readily. When electricity issues from a conductor, remote from 
an oppositely excited one, it gives an absolutely silent dis- 
charge, showing at the point of escape a pale blue luminosity called 
electric glow, or if it escapes from points it shows a star-like centre of 
light. It can be seen in the dark by placing a point on the excited 
conductor of a static-electric machine. 

Synonyms — Silent Discharge — Glow Discharge. 

Discharge, Conductive. A discharge of a static charge by 
conduction through a conductor. 

Discharge, Convective. The discharge of static electricity from 
an excited conductor through air or rarefied gas ; it is also called 
the quiet or silent discharge. The luminous effect in air or gas at 
atmospheric pressures takes the form of a little brush from a small 
positive electrode ; the negative shows a star. The phenomena of 
Gassiot's cascade, the philospher's egg and Geissler tubes, all of 
which may be referred to, are instances of convective discharge. 

Discharge, Dead Beat. A discharge that is not oscillatory in 
character. 

Discharge, Disruptive. A discharge of a static charge through 
a dielectric. It involves mechanical perforation of the dielectric, 
and hence the mere mechanical strength of the latter has much to 
do with preventing it. A disruptive discharge is often oscillatory 
in character ; this is always the case with the discharge of a Ley- 
den jar. 



i88 STANDARD ELECTRICAL DICTIONARY. 

Discharge, Duration of. The problem of determining this 
factor has been attacked by various observers. Wheatstone with 
his revolving mirror found it to be gwotf second. Fedderson, by 
interposing resistance, prolonged it to yoVoo* and again to T ^f §o 
second. Lucas & Cazin made it from 26 to 47 millionths of a second. 
All these experiments were performed with Ley den jars. 

Discharge, Impulsive. A disruptive discharge produced be- 
tween conductors by suddenly produced potential differences. The 
self-induction of the conductor plays an especially important part 
in discharges thus produced. 

Discharge, Lateral, (a) A lightning discharge, which some- 
times takes place between a light ing rod and the building on 
which it is. 

(6) In the discharge of a Leyden jar or condenser the discharge 
which takes the alternative path, q. v. 

Discharge, Oscillatory. The sudden or disruptive discharge of 
a static condenser, such as a Leyden jar, or of many other charged 
conductors, is oscillatory in character. The direction of the currents 
rapidly changes, so that the discharge is really an alternating cur- 
rent of excessively short total duration. The discharge sends 
electro-magnetic waves through the ether, which are exactly anal- 
ogous to those of light but of too long period to affect the eye. 

Synonym — Surging Discharge. 

Discharger. An apparatus for discharging Leyden jars. It con- 
sists of a conductor terminating in balls, and either jointed like a 




Fig". 132. Discharger. 

tongs or bent with a spring-action, so that the balls can be set at 
distances adapted to different sized jars. It has an insulating 



STANDARD ELECTRICAL DICTIONARY. 189 

handle or a pair of such. In use one ball is brought near to the 
coating and the other to the spindle ball of the jar. When nearly 
or quite in contact the jar discharges. 

Synonyms — Discharging Rod — Discharging Tongs. 

Discharger, Universal. An apparatus for exposing substances 
to the static discharge spark. It consists of a base with three insu- 
lating posts. The central post carries an ivory table to support the 
object. The two side posts carry conducting rods, terminating in 
metal balls, and mounted with universal joints. A violent shock 
can be given to any object placed on the table. 

Synonym — Henley's Universal Discharger. 

Discharge, Silent. This term is sometimes applied to the glow 
or brush discharge and sometimes to the condition of electric efflu- 
vium. (See Discharge, Brush — Effluvium, Electric.) 

Discharge, Spark. The discontinuous discharge of high tension 
electricity through a dielectric or into the air produces electric sparks. 
These are quite strongly luminous, of branching sinuous shape, and 
in long sparks the luminosity varies in different parts of the same 
spark. A sharp noise accompanies each spark. High density of 
charge is requisite for the formation of long sparks. 

Disconnection. The separation of two parts of, or opening a cir- 
cuit, as by turning a switch, unscrewing a binding screw, or the 
like. The term is sometimes used to indicate a class of faults in 
telegraph circuits. Disconnections may be total, partial or inter- 
mittent, and due to many causes, such as open or partially replaced 
switches, oxidized or dirty contact points, or loose joints. 

Displacement, Electric. A conception of the action of charg- 
ing a dielectric. The charge is all on the surface. This fact being 
granted, the theory of displacement holds that charging a body is 
the displacing of electricity, forcing it from the interior on to the 
surface, or vice versa, producing a positive or negative charge by 
displacement of electricity. While displacement is taking place in 
a dielectric there is assumed to be a movement or current of elec- 
tricity called a displacement current. 

Disruptive Tension. When the surface of a body is electrified, 
it tends to expand, all portions of the surface repelling each other. 
The film of air surrounding such a body is electrified too, and is 
subjected to a disruptive tension, varying in intensity with the 
square of the density. 

Dissimulated Electricity. The electricity of a bound charge. 
(See Charge, Bound.) 

Dissociation, The separation of a chemical compound into its 



i 9 o STANDARD ELECTRICAL DICTIONARY. 

elements by a sufficiently high degree of heat. All compounds are 
susceptible of dissociation, so that it follows that combustion is 
impossible at high temperatures. 

Distance, Critical, of Alternative Path. The length of air 
gap in an alternative path whose resistance joined to the impedance 
of the rest of the conductors of the path just balances the impedance 
of the other path. 

Distance, Sparking. The distance between electrodes, which a 
spark from a given Ley den jar or other source will pass across. 
Synonym — Explosive Distance. 

Distillation. The evaporation of a liquid by heat, and some- 
times in a vacuum, followed by condensation of the vapors, which 
distil or drop from the end of the condenser. It is claimed that 
the process is accelerated by the liquid being electrified. 

Distributing Box. In an electric conduit system, a small iron 
box provided for giving access to the cable for the purpose of mak- 
ing house and minor connections. 

Synonym — Hand Hole. 

Distributing Switches. Switch systems for enabling different 
dynamos to supply different lines of a system as required. Spring 
jacks, q. v., are used for the lines, and plug switches for the dynamo 
leads. Thus, dynamos can be thrown in or out as desired, without 
putting out the lights. 

Distribution of Electric Energy, Systems of. The systems of 
electric current distribution from central stations or from private gen- 
erating plants, mechanical or battery, the latter primary or secondary. 
They include in general the alternating current system and direct 
current systems. Again, these may be subdivided into series and 
multiple arc, multiple-series and series-multiple distribution, and 
the three, four, or five wire system may be applied to multiple arc 
or multiple series systems. (See Alternating Current — Current 
System — Multiple Arc — Multiple Series — Series Multiple — Three 
Wire System.) 

Door Opener, Electric. An apparatus for opening a door by 
pushing back the latch. A spring then draws the door open, and it 
is closed against the force of the spring by the person entering. 
Electro-magnetic mechanism actuates the latch, and is operated by 
a switch or press-button. Thus a person on the upper floor can 
open the hall door without descending. 

Dosage, Galvanic. In electro-therapeutics the amount of electric 
current or discharge, and duration of treatment given to patients. 



STANDARD ELECTRICAL DICTIONARY. 191 

Double Carbon Arc Lamp. An arc lamp designed to burn all 
night, usually constructed with two parallel sets of carbons, one set 
replacing the other automatically, the current being switched from 
the burnt out pair to the other by the action of the mechanism of 
the lamp. 

Double Fluid Theory. A theory of electricity. Electricity is 
conveniently treated as a fluid or fluids. According to the double 
fluid hypothesis negative electricity is due to a preponderance of 
negative fluid and vice versa. Like fluid repels like, and unlike 
attracts unlike ; either fluid is attracted by matter ; the presence in 
a body of one or the other induces electrification ; united in equal 
proportions they neutralize each other, and friction, chemical 
decomposition and other causes effect their separation. The hypo- 
thesis, while convenient, is overshadowed by the certainty that 
electricity is not really a fluid at all. (See Single Fluid Theory 
— Fluid, Electric.) 

Synonym — Symmer's Theory. 

Double Fluid Voltaic Cell. A cell in which two fluids are used, 
one generally as depolarizer surrounding the negative plate, the 
other as excitant surrounding the positive plate. A porous dia- 
phragm or difference in specific gravities is used to keep the solu- 
tions separate and yet permit the essential electrolytic diffusion. 
Grove's Cell, Bunsen's Cell, and DanielVs Cell, all of which may 
be referred to, are of this type, as are many others. 

Double Wedge. A plug for use with a spring-jack. It has con- 
nection strips at its end and another pair a little distance back 
therefrom, so that it can make two loop connections at once. 

Synonym — Double Plug. 

Doubler. A continuously acting electrophorous ; an early pre- 
decessor of the modern electric machines. It is now no longer used. 

D. P. Abbreviation for Potential Difference. 

Drag. The pull exercised by a magnetic field upon a conductor 
moving through it pr upon the motion of an armature in it. 

Dreh=strom. (German) Rotatory currents ; a system of currents 
alternating in periodic succession of phases and producing a rotatory 
field. (See Field, Rotatory — Multiphase Currents,) 

Drill Electric. A drill for metals or rock worked by an elec- 
tro-magnetic motor. For metals a rotary motion, for rocks a 
reciprocating or percussion action is imparted. It is used by ship- 
builders for drilling holes in plates which are in place in ships, as 
its flexible conductors enabl« it to be placed anywhere. For rock- 
drilling a solenoid type of construction is adopted, producing rapid 
percussion. 



192 



STANDARD ELECTRICAL DICTIONARY. 



Drip Loop. A looping downward of wires entering a building, 
so that rain water, as it runs along the wire, will drip from the low- 
est part of the loop instead of following the wire into or against the 
side of the building. 

Driving Horns. Projections on the periphery of an armature 
of a dynamo for holding the winding in place and preventing its 
displacement. Various arrangements have been adopted. They 
are sometimes wedges or pins and are sometimes driven into spaces 
left in the drum core. The toothed disc armature cores make up 
an armature in which the ridges formed by the teeth form practic- 
ally driving horns. 

Dronier's Salt. A substance for solution for use in bichromate 
batteries. It is a mixture of one-third potassium bichromate and 
two-thirds potassium bisulphate. It is dissolved in water to make 
the exciting fluid. 

Drop, Automatic. A switch or circuit breaker, operating to 
close a circuit by dropping under the influence of gravity. It is 
held up by a latch, the circuit remaining open, until the latch is 




The Magic Drum. 



released by a current passing through an electro-magnet. This 
attracting an armature lets the drop fall. As it falls it closes a local 
or second circuit, and thus may keep a bell ringing until it is 



STANDARD ELECTRICAL DICTIONARY. 193 

replaced by hand. It is used in burglar alarms, its function 
being to keep a bell ringing even though the window or door by 
which entrance was made is reclosed. 

Drum, Electric. A drum with a mechanism within for striking 
the head with a hammer or some equivalent method so as to be 
used as a piece of magical apparatus. In the one shown in the cut 
a sort of telephone action is used to produce the sound, the elec- 
tro-magnet D and armature being quite screened from observation 
through the hole. (See Fig. 133) A ring, C, shown in Fig. 133, 
with two terminals, the latter shown by the unshaded portions a a y 
and a suspending hook £, also with two terminals, and two sus- 
pending conductors A> B, carry the current to the magnet. A 
sudden opening or closing of the circuit produces a sound. 

Dub's Laws. 1. The magnetism excited at any transverse 
section of a magnet is proportional to the square root of the dis- 
tance between the given section and the end. 

2. The free magnetism at any given transverse section of a 
magnet is proportional to the difference between the square root of 
half the length of the magnet and the square root of the distance 
between the given section and the nearest end. 

Duct. The tube or compartment in an electric subway for the 
reception of a cable. (See Conduit ', Electric Subway.) 

Dyad. A chemical term ; an element which in combination 
replaces two monovalent elements ; one which has two bonds or is 
bivalent. 

Dyeing, Electric. The producing mordanting or other dyeing 
effects on goods in dyeing by the passage of an electric current. 

Dynamic Electricity. Electricity of relatively low potential 
and large quantity ; current electricity as distinguished from static 
electricity ; electricity in motion. 

Dynamo, Alternating Current. A dynamo-electric machine for 
producing an alternating current ; an alternator. They are classi- 
fied by S. P. Thompson into three classes — I. Those with stationary 
field-magnet and rotating armature. II. Those with rotating, field- 
magnet and stationary armature. III. Those with both field 
magnet part and armature part stationary, the amount of magnetic 
induction from the latter through the former being caused to vary 
or alternate in direction by the revolution of appropriate pieces of 
iron, called inductors. Another division rests on whether they 
give one simple alternating current, a two phase current, or 
whether they give multiphase currents. (See Current, Alternat- 
ing — Currents , Multiphase.) 

A great many kinds of alternators have been constructed. Only 



194 



STANDARD ELECTRICAL DICTIONARY. 



an outline of the general theory can be given here. They are gener- 
ally multipolar, with north and south poles alternating around the 
field. The armature coils, equal in number in simple current 
machines, to the poles, are wound in opposite senses, so that the 
current shall be in one direction, though in opposite senses, in all 
of them at any one time. As the armature rotates the coils are all 
approaching their poles* at one time and a current in one sense is 
induced in every second coil, and one in the other sense in the 
other coils. They are all in continuous circuit with two open ter- 
minals, each connected to its own insulated connecting ring on the 
shaft. As the coils pass the poles and begin to recede from them 




FiR. 134. 



Alternating Current Dynamo with Separate Exciter Mounted 
on Main Shaft. 



the direction changes, and the current goes in the other direction 
until the next poles are reached and passed. Thus there are as 
many changes of direction of current per rotation as there are coils 
in the armature or poles in the field. 



STANDARD ELECTRICAL DICTIONARY. 



195 



The field-magnets whose windings may be in series are often 
excited by a separate direct current generation. Some are self- 
exciting, one or more of the armature coils being separated from 
the rest, and connected to a special commutator, which rectifies its 
current. 

By properly spacing the coils with respect to the poles of the 
field, and connecting each set of coils by itself to separate connect- 
ing rings, several currents can be taken from the same machine, 




-I- 5 *? 



Fig. 



135. Diagram of Arrangement of Armature Coils and 
Rings in an Alternating Current Dynamo. 



Collecting 



which currents shall have a constant difference in phase. It would 
seem at first sight that the same result could be attained by using 
as many separate alternators as there were currents to be produced. 
But it would be almost impossible to preserve the exact relation of 
currents and current phase where each was produced by its own 
machine. The currents would overrun each other or would lag 
behind. In a single machine with separate sets of coils the relation 
is fixed and invariable. 

Dynamo, Alternating Current, Regulation of. Transform- 
ers, converters, or induction coils are used to regulate alternating 
current dynamos, somewhat as compound winding is applied in the 
case of direct-current dynamos. The arrangement consists in con- 
necting the primary of an induction coil or transformer into the exter- 
nal circuit with its secondary connected to the field circuit. Thus the 
transformer conveys current to the field picked up from the main 
circuit, and represents to some extent the shunt of a direct-cur- 
rent machine. 

Dynamo, Commercial Efficiency of. The coefficient, q. v., 
obtained by dividing the mechanically useful or available work 



196 



STANDARD ELECTRICAL DICTIONARY. 



of a dynamo by the mechanical energy absorbed by it. This only 
includes the energy available in the outer circuit, for doing useful 
work. 

Dynamo* Compound. A compound wound dynamo ; one which 
has two coils on its field magnet ; one 
winding is in series with the external 
circuit and armature ; the other wind- 
ing is in parallel with the armature 
winding, or else with the armature 
winding and field winding, both in 
series. (See Winding, Long Shunt — 
Winding, Short Shunt.) 

Such a dynamo is, to a certain ex- 
tent, self - regulating, the two coils 
counteracting each other, and bringing 
about a more regular action for varying 
currents than that of the ordinary shunt 
or series dynamo. 

The extent of the regulation of such 
a machine depends on the proportions 
given its different parts. However 
good the self-regulating may be in a compound wound machine, it 
can only be perfect at one particular speed. 

To illustrate the principle on which the approximate regulation 
is obtained the characteristic curve diagram may be consulted. 




Compound Wound 
Dynamo. 




o Ohms fc x 

Fig. 137. Curves of Series and Shunt Windings Superimposed. 

One curve is the curve of a series winding, the other that of a 
shunt winding, and shows the variation of voltage in each with 
lesistance in the external or working circuit. The variation is 



STANDARD ELECTRICAL DICTIONARY. 197 

opposite in each case. It is evident that the two windings could be 
so proportioned on a compound machine that the resultant of the 
two curves would be a straight line. This regulation would then be 
perfect and automatic, but only for the one speed. 

Dynamo, Direct Current. A dynamo giving a current of un- 
varying direction, as distinguished from an alternator or alternating 
current dynamo. 

Dynamo, Disc. A dynamo with a disc armature, such as Paci- 
notti's disc, q. v. (See also Disc, Armature.) The field magnets 
are disposed so that the disc rotates close to their poles, and the 
poles face or are opposite to the side or sides of the disc. The active 
leads of wire are those situated on the face or faces of the disc. 




Fig. 138. Polechko's Disc Dynamo. 

Dynamo=electric Machine. A machine driven by power, gen- 
erally steam power, and converting the mechanical energy 
expended on driving it into electrical energy of the current form. 
The parts of the ordinary dynamo may be summarized as follows : 
First, A circuit as complete as possible of iron. Such circuit is 
composed partly of the cores of an electro-magnet or of several 
electro-magnets, and partly of the cylindrical or ring-shaped core of 
an armature which fits as closely as practicable between the magnet 
ends or poles which are shaped so as to partly embrace it. Second, 
of coils of insulated wire wound upon the field-magnet cores. 
When these coils are excited the field-magnets develop polarity, 
and the circuit just spoken of becomes a magnetic circuit, inter- 
rupted only by the air gaps between the poles and armatures. 
Thirdly, of coils of insulated wire upon the armature core. These 
coils when rotated in the magnetic field cut magnetic lines of force 



198 STANDARD ELECTRICAL DICTIONARY. 

and develop electro-motive force. Fourthly, of collecting mechan- 
ism, the commutator in direct current dynamos, attached to the 
armature shaft and rotating with it. This consists of insulated 
rings, or segments of rings to which the wire coils of the armature 
are connected, and on which two springs of copper or plates of car- 
bon or some other conductor presses. The electro-motive force 
developed by the cutting of lines of force, by the wires of the 
armature, shows itself as potential difference between the two 
springs. If the ends of a conductor are attached, one to each of 
these brushes, the potential difference will establish a current 
through the wire. By using properly divided and connected seg- 
ments on the commutator the potential difference and consequent 
direction of the current may be kept always in the same sense or 
direction. It is now clear that the external wire may be connected 
with the windings of the field-magnet. In such case the excite- 
ment of the field-magnets is derived from the armature and the 
machine is self-excited and entirely self-contained. 

The above is a general description of a dynamo. Sometimes 
the coils of the field-magnets are not connected with the arma- 
ture, but derive their current from an outside source. Such are 
termed separately excited dynamos. 

Some general features of dynamo generators may be seen in the 
definitions under this head and elsewhere. The general conception 
is to cut lines of force with a conductor and thus generate electro- 
motive force, or in some way to change the number of lines of 
force within a loop or circuit with the same effect. 

Dynamo, Electroplating. A dynamo designed for low poten- 
tial and high current intensity. They are wound for low resistance, 
frequently several wires being used in parallel, or ribbon, bar or rect- 
angular conductors being employed. They are of the direct current 
type. They should be shunt wound or they are liable to reverse. They 
are sometimes provided with resistance in the shunt, which is 
changed as desired to alter the electro-motive force. 

Dynamo, Equalizing. A combination for three and five-wire 
systems. A number of armatures or of windings on the same 
shaft are connected across the leads. If the potential drops at any 
pair of mains, the armature will begin to be driven by the other 
mains, acting to an extent as an element of a motor, and will raise 
the potential in the first pair. 

Dynamo, Far Leading. A motor dynamo, used to compensate 
the drop of potential in long mains. Into the mains at a distant 
point a series motor is connected, driving a dynamo placed in 
shunt across the mains. The dynamo thus driven raises the poten- 
tial difference between the two mains. 



STANDARD ELECTRICAL DICTIONARY. 



199 



Dynamograph. A printing telegraph in which the message is 
printed at both transmitting and receiving ends. 

Dynamo, Inductor. A generator in which the armature or cur- 
rent-generating windings are all comprised upon the poles of the 
field magnets. Masses of iron, which should be laminated and are 
the inductors, are carried past the field magnet poles concentrating 
in their passage the lines of force, thus inducing currents in the 
coils. In one construction shown in the cut the field magnets a, a 
• ■ are U shaped and are arranged in a circle, their poles pointing 
inwards. A single exciting coil c, c * * * is wound around the circle 
in the bend of the U-shaped segments. The poles carry the arma- 
ture coils e, e ' * • . The laminated inductors i, i ■ * * are mounted 
on a shaft S s by spiders k, to be rotated inside the circle of magnets, 
thus generating an alternating current. 

Synonym — Inductor Generator. 




Fig. 139. Inductor Dynamo. 

Dynamo, Interior Pole. A dynamo with a ring armature, with 
field magnet pole pieces which extend within the ring. 



200 STANDARD ELECTRICAL DICTIONARY. 

Dynamo, Iron Clad. A dynamo in which the iron of the field 
magnet is of snch shape as to enclose the field magnet coils as well 
as the armature. 

Dynamometer. A device or apparatus for measuring force applied, 
or rate of expenditure of energy by, or work done in a given time 
by a machine. A common spring balance can be used as a force 
dynamometer, viz : to determine how hard a man is pulling and 
the like. The steam engine indicator represents an energy-dyna- 
mometer of the graphic type, the instrument marking an area 
whence, with the aid of the fixed factors of the engine, the work 
done may be determined. Prony's Brake, q. v., is a type of the 
friction dynamometer, also of the energy type. In the latter type 
during the experiment the whole power must be turned on or be 
expended on the dynamometer. 

Dynamo, Motor. A motor dynamo is a machine for (a) con- 
verting a continuous current at any voltage to a continuous current 
of different strength at a different voltage or for (6) transforming a 
continuous current into an alternating one, and vice versa. 

For the first type see Transformer, Continuous Current; for the 
second type see Transformer ; Alternating Current. 

Dynamo, Multipolar. A dynamo having a number of field 
magnet poles, not merely a single north and a single south pole. 
The field magnet is sometimes of a generally circular shape with 
the poles arranged radially within it, the armature revolving 
between the ends. 

Dynamo, Non=poIar. A name given by Prof. George Forbes to 
a dynamo invented by him. In it a cylinder of iron rotates within 
a perfectly self-contained iron-clad field magnet. The current 
is taken off by brushes bearing near the periphery, at two 
extremities of a diameter. A machine with a disc 18 inches in 
diameter was said to give 3,117 amperes, with 5.8 volts E. M. F. 
running at 1,500 revolutions per second. The E. M. F. of such 
machines varies with the square of the diameter of the disc or 
cylinder. 

Dynamo, Open Coil. A dynamo the windings of whose arma- 
tures may be grouped in coils, which are not connected in series, 
but which have independent terminals. These terminals are 
separate divisions of the commutator and so spaced that the collect- 
ing brushes touch each pair belonging to the same coil simultaneously. 
As the brushes come in contact with the sections forming the ter- 
minals they take current from the coil in question. This coil is 
next succeeded by another one, and so on according to the number 
of coils employed. 

Dynamo, Ring. A dynamo the base of whose field magnets is a 



STANDARD ELECTRICAL DICTIONARY. 



20I 



ring in general shape, or perhaps an octagon, and with poles 
projecting inwardly therefrom. 

Dynamo, Coupling of. Dynamos can be coupled exactly like 
batteries and with about the same general results. An instance of 
series coupling would be given by the dynamos in the three wire 
system when no current is passing through the neutral wire, and 
when the lamps on each side of it are lighted in equal number. 

Dynamo, Self =exciting. A dynamo which excites its own field. 
The majority of dynamos are of this construction. Others, espe- 
cially alternating current machines, are separately excited, the 
field magnets being supplied with current from a separate dynamo 
or current generator. 

Dynamo, Separate Circuit. A dynamo in which the field 
magnet coils are entirely disconnected from the main circuit, and 
in which current for the field is supplied by special coils carried 
for the purpose by the same armature, or by a special one, in either 
case a special commutator being provided to collect the current. 

Dynamo, Separately Excited. A dynamo whose field magnets 
are excited by a separate current generator, such as a dynamo or 
even a battery. Alternating current dynamos are often of this 
construction. Direct current dynamos are not generally so. The 
term is the opposite of self-exciting. 




Fig. 140. Series Dynamo. 

Dynamo, Series. A dynamo whose armature, field winding, 
and external circuit are all in series. 



202 



STANDARD ELECTRICAL DICTIONARY. 



In such a dynamo short circuiting or lowering the resistance of 
the external circuit strengthens the field, increases the electro-mo- 
tive force and current strength and may injure the winding by 
heating the wire, and melting the insulation. 

Dynamo, Shunt. A dynamo whose field is wound in shunt 
with the external circuit. Two leads are taken from the brushes ; 
one goes around the field magnets to excite them ; the other is the 
external circuit. 

In such a dynamo the lowering of resistance on the outer circuit 
takes current from the field and lowers the electro-motive force of 
the machine. Short circuiting has no heating effect. 




Fig. 141. Shunt Dynamo. 

Dynamo, Single Coil. A dynamo whose field magnet is 
excited by a single coil. Several such have been constructed, with 
different shapes of field magnet cores, in order to obtain a proper 
distribution of poles. 

Dynamo, Tuning Fork. A dynamo in which the inductive or 
armature coils were carried at the ends of the prongs of a gigantic 
tuning fork, and were there maintained in vibration opposite 
the field magnets. It was invented by T. A. Edison, but never 
was used. 

Dynamo, Uni=polar. A dynamo in which the rotation of a 
conductor effects a continuous increase in the number of lines cut, 



STANDARD ELECTRICAL DICTIONARY. 203 

by the device of arranging one part of the conductor to slide on or 
around the magnet. (S. P. Thomson.) Faraday's disc is the earliest 
machine of this type. 

Dyne. The C. G. S. or fundamental unit of force. It is the 
force which can impart an acceleration of one centimeter per 
second to a mass of one gram in one second. It is equal to about 
1-98 1 the weight of a gram, this weight varying with the latitude. 

Earth, (a) The earth is arbitrarily taken as of zero electrostatic 
potential. Surfaces in such condition that their potential is un- 
changed when connected to the earth are said to be of zero poten- 
tial. All other surfaces are discharged when connected to the 
earth, whose potential, for the purposes of man at least, never 
changes. 

(b) As a magnetic field of force the intensity of the earth's field 
is about one-half a line of force per square centimeter. 

(c) The accidental grounding of a telegraph line is termed an 
earth, as a dead, total, partial, or intermittent earth, describing the 
extent and character of the trouble. 

Earth, Dead. A fault, when a telegraph or other conductor is 
fully connected to earth or grounded at some intermediate point. 
Synonyms — Solid Earth — Total Earth. 

Earth, Partial. A fault, when a telegraph or other conductor 
is imperfectly connected to earth or grounded at some intermediate 
point. 

Earth Plate. A plate buried in the earth to receive the ends of 
telegraph lines or other circuits to give a ground, q. v. A copper 
plate is often used. A connection to a water or gas main gives an 
excellent ground, far better than any plate. When the plate oxidizes 
it is apt to introduce resistance. 

Earth Return. The grounding of a wire of a circuit at both 
ends gives the circuit an earth return. 

Earth, Swinging. A fault, when a telegraph or other conduc- 
tor makes intermittent connection with the earth. It is generally 
attributable to wind action swinging the wire, whence the name. 

Ebonite. Hard vulcanized India rubber, black in color. Specific 
resistance in ohms per cubic centimeter at 46 C. (115 E.): 34 X 
io 15 (Ayrton) ; specific inductive capacity, (air = 1) : 2.56 (Wiill- 
ner) ; 2.76 (Schiller); 3.15 (Boltzmann). It is used in electrical 
apparatus for supporting members such as pillars, and is an excel- 
lent material for frictional generation of potential. Its black color 
gives it its name, and is sometimes made a point of distinction from 
Vulcanite, q. v. 



204 



STANDARD ELECTRICAL DICTIONARY. 



Economic Coefficient. The coefficient of electric efficiency. 
(See Efficiency, Electric) 

Edison Effect. A continuous discharge resulting in a true cur- 
rent which takes place between a terminal of an incandescent lamp 
filament and a plate placed near it. The lamp must be run at 
a definitely high voltage to obtain it. 

Ediswan. An abbreviation for Edison-Swan ; the trade name 
of the incandescent lamp used in Great Britain, and of other 
incandescent system apparatus. 

Eel, Electric {Gymnotus Electricus). An eel capable of effecting 
the discharge of very high potential 
electricity, giving painful or dangerous 
shocks. Its habitat is the fresh water, 
in South America. Faraday investigated 
it and estimated its shock as equal to that 
from fifteen Iyeyden jars, each of i % square 
feet of coating. (See Animal Electricity 
and Ray, Electric.) 

Effect, Counter=inductive. A counter- 
electro-motive force due to induction, and 
opposing a current. 

Efficiency. The relation of work done 
to energy absorbed. A theoretically perfect machine would have the 
maximum efficiency in which the two qualities named would be 
equal to each other. Expressed by a coefficient, q. v. , the efficiency 
in such case would be equal to i. If a machine produced but half 
the work represented by the energy it absorbed, the rest disappearing 
in wasteful expenditure, in heating the bearings, in overcoming the 
resistance of the air and in other ways, its efficiency would be 
expressed by the coefficient yi. or .5, or if onei hundred was the basis, 
by fifty per centum. There are a number of kinds of efficiencies of 
an electric generator which are given below. 

Efficiency, Commercial. Practical efficiency of a machine, ob- 
tained by dividing the available output of work or energy of a 
machine by the energy absorbed by the same machine. Thus in 
a dynamo part of the energy is usefully expended in exciting the 
field magnet, but this energy is not available for use in the outer 
circuit, is not a part of the output, and is not part of the dividend. 

If M represents the energy absorbed, and W the useful or avail- 
able energy, the coefficient of commercial efficiency is equal to 
W/M. M is made up of available, unavailable and wasted (by 
Foucault currents, etc.,) energy. Calling available energy W, 




Fig. 142. Gymnotus 
Electricus. 



STANDARD ELECTRICAL DICTIONARY. 205 

unavailable but utilized energy w, and wasted energy m, the 
expression for the coefficient of commercial efficiency becomes 

W 

W + w + m when M = W -f" w-\-m 
Synonym — Net efficiency. 

Efficiency, Electrical. In a dynamo or generator the relation 
of total electric energy produced, both wasted and useful or avail- 
able to the useful or available electrical energy. If we call W the 
useful electric and w the wasted electric energy, the coefficient of 
electrical effiiciency is equal to W 

W + w 
Synonyms — Intrinsic Efficiency — Economic Coefficient — Coeffi- 
cient of Electrical Efficiency. 

Efficiency of Conversion. In a dynamo or generator the 
relation of energy absorbed to total electric energy produced. Part 
of the electric energy is expended in producing the field and in 
other ways. Thus a generator with high efficiency of conversion 
may be a very poor one, owing to the unavailable electric energy 
which it produces. The coefficient of Efficiency of Conversion is 
obtained by dividing the total electric energy produced by the 
energy absorbed in working the dynamo. If M represents the 
energy absorbed, or work done in driving the dynamo or generator, 
W the useful electric, and w the wasted electrical energy, then the 
coefficient of efficiency of 'conversion is equal to W 4- w 

M 

In the quantity M are included besides available ( W) and unavaila- 
ble (w) electric energy, the totally wasted energy due to Foucault 
currents, etc., calling the latter m, the above formula may be given 

W + w 
W + w + m 

This coefficient may refer to the action of a converter, q. v. , in 

the alternating system. 
Synonym — Gross Efficiency. 

Efficiency of Secondary Battery, Quantity. The coeffi- 
cient obtained by dividing the ampere-hours obtainable from a 
secondary battery by the ampere hours required to charge it. 

Efficiency of Secondary Battery, Real. The coefficient 
obtained by dividing the energy obtainable from a secondary battery 
by the energy absorbed in charging it. The energy is conven- 
iently taken in watt-hours and includes the consideration of the 
spurious voltage. (See Battery, Secondary.) 



206 STANDARD ELECTRICAL DICTIONARY. 

Efflorescence. The appearence of a dry salt upon the walls of 
a vessel containing a solution above the normal water-line from 
evaporation of a liquid. It appears in battery jars and in battery 
carbons, in the latter interfering with the electrical connections, 
and oxidizing or rusting them. (See Creeping.) 

Effluvium, Electric. When a gas is made to occupy the position 
of dielectric between two oppositely electrified surfaces a peculiar 
strain or condition of the dielectric is produced, which promotes 
chemical change. The condition is termed electrical effluvium or 
the silent discharge. By an apparatus specially constructed to 
utilize the condition large amounts of ozone are produced. 

Synonym — Silent Discharge. 

Elastic Curve. A crude expression for a curve without projec- 
tions or sudden sinuosities ; such a curve as can be obtained by 
bending an elastic strip of wood. 

Electrepeter. An obsolete name for a key, switch or pole 
changer of any kind. 

Elasticity, Electric. The phenomenon of the dielectric is 
described under this term. When a potential difference is established 
between two parts of the dielectric, a flow of electricity displace- 
ment current starts through the dielectric, which current is due to 
the electric stress, but is instantly arrested by what has been 
termed the electric elasticity of the dielectric. This is expressed 

by —— and in any substance is inversely proportional 

electric strain 
to the specific inductive capacity. 

Electricity. It is impossible in the existing state of human 
knowledge to give a satisfactory definition of electricity. The 
views of various authorities are given here to afford a basis for 
arriving at the general consensus of electricians. 

We have as yet no conception of electricity apart from the elec- 
trified body ; we have no experience of its independent existence. 
... (J. E. H. Gordon.) 

What is Electricity ? We do not know, and for practical pur- 
poses it is not necesssary that we should know. (Sydney F. 
Walker.) 

Electricity is one of those hidden and 

mysterious powers of nature which has thus become known to us 
through the medium of effects. (Weale's Dictionary of Terms.) 

This word Electricity is used to express more particularly the 
cause, which even to-day remains unknown, of the phenomena 
that we are about to explain. (Am£d£e Guillemin.) 



STANDARD ELECTRICAL DICTIONARY. 207 

Electricity is a powerful physical agent which manifests itself 
mainly by attractions and repulsions, but also by luminous and 
heating effects, by violent commotions, by chemical decomposi- 
tions, and many other phenomena. Lnlike gravity, it is not in- 
herent in bodies, but it is evoked in them by a variety of causes 
(Ganot's Physics.) 

Electricity and magnetism are not forms of energy ; neither are 
they forms of matter. They may, perhaps, be provisionally denned 
as properties or conditions of matter ; but whether this matter be 
the ordinary matter, or whether it be, on the other hand, that all- 
pervading ether by which ordinary matter is surrounded, is a 
question which has been under discussion, and which now may be 
fairly held to be settled in favor of the latter view. (Daniell's 
Physics. ) 

The name used in connection with an extensive and important 
class of phenomena, and usually denoting the unknown cause of the 
phenomena or the science that treats of them. (Imperial Dic- 
tionary.) 

Electricity is the imponderable physical agent, 

cause, force or the molecular movement, by which, under certain 
conditions, certain phenomena, chiefly those of attractio?i and 
repulsion, are produced. (John Angell.) 

It has been suggested that if anything can rightly be called 
" electricity," this must be the ether itself; and that all electrical 
and magnetic phenomena are simply due to changes, strains and 
motions in the ether. Perhaps negative electrification .... 
. means an excess of ether, and positive electrification a 
defect of ether, as compared with the normal density. (W. 
Larden.) 

Electricity is the name given to the supposed agent producing the 
described condition (i. e. electrification) of bodies. (Fleeming 
Jenkin.) 

There are certain bodies which, when warm and dry, acquire by 
friction, the property of attracting feathers, filaments of silk or 
indeed any light body towards them. This property is called 
Electricity, and bodies which possess it are said to be electrified. 
(Linnaeus Cumming.) 

What electricity is it is impossible to say, but for the present it is 
convenient to look upon it as a kind of invisible something which 
pervades all bodies. (W. Perren May cock.) 

What is electricity ? Xo one knows. It seems to be one mani- 
festation of the energy which fills the universe and which appears 
in a variety of other forms, such as heat, light, magnetism, chemi- 
cal affinity, mechanical motion, etc. (Park Benjamin.) 

The theory of electricity adopted throughout these lessons is, 



208 STANDARD ELECTRICAL DICTIONARY. 

that electricity, whatever its true nature, is one, not two ; that this 
Electricity, whatever it may prove to be, is not matter, and is not 
energy ; that it resembles both matter and energy in one respect, 
however, in that it can neither be created nor destroyed. (Syl- 
vanus P. Thomson.) 

In Physics a name denoting the cause of an important class of 
phenomena of attraction and repulsion, chemical decomposition, 
etc., or, collectively, these phenomena themselves. (Century Dic- 
tionary.) 

A power in nature, often styled the electric fluid, exhibiting 
itself, when in disturbed equilibrium or in activity, by a circuit 
movement, the fact of direction in which involves polarity, or op- 
position of properties in opposite directions; also, by attraction for 
many substances, by a law involving attraction between sub- 
stances of unlike polarity, and repulsion between those of like ; by 
exhibiting accumulated polar tension when the circuit is broken ; 
and by producing heat, light, concussion, and often chemical 
changes when the circuit passes between the poles, or through any 
imperfectly conducting substance or space. It is evolved in any 
disturbance of molecular equilibrium, whether from a chemical, 
physical, or mechanical cause. (Webster's Dictionary.) 

In point of fact electricity is not a fluid at all, and only in a few 
of its attributes is it at all comparable to a fluid. Let us rather con- 
sider electricity to be a condition into which material substances 
are thrown (Slingo & Brooker.) 

Electricity, Cal. The electricity produced in the secondary of a 
transformer by changes of temperature in the core. This is in 
addition to the regularly induced current. 

Synonym — Acheson Effect. 

Electrics. Substances developing electrification by rubbing or 
friction ; as Gilbert, the originator of the term, applied it, it would 
indicate dielectrics. He did not know that, if insulated, any substance 
was one of his ' ' electrics. ' ' A piece of copper held by a glass handle 
becomes electrified by friction. 

Electrification. The receiving or imparting an electric charge 
to a surface ; a term usually applied to electrostatic phenomena. 

Electrization. A term in electro-therapeutics ; the subjection of 
the human system to electric treatment for curative, tonic or diag- 
nostic purposes. 

Electro=biology. The science of electricity in its relation to 
the living organism, whether as electricity is developed by the 
organism, or as it affects the same when applied from an external 
source. 



STANDARD ELECTRICAL DICTIONARY. 209 

Electro=capillarity. The relations between surface tension, the 
potential difference and the electrostatic capacity of fluids in con- 
tact. Although nominally in contact such surfaces are separated by 
about one-twenty-millionth of a centimeter ( -g-oowoo inch) ; thus a 
globule of mercury and water in which it is immersed constitute an 
electrostatic accumulator of definite electrostatic capacity. Again 
the mercury and water being in electric connection differ in poten- 
tial by contact (see Contact Theory). A definite surface tension is 
also established. Any change in one of these factors changes the 
other also. A current passed through the contact surfaces will 
change the surface tension and hence the shape of the mercury 
globule. Shaking the globule will change its shape and capacity 
and produce a current. Heating will do the same. (See Electro- 
meter, Capillary ; and Telephone, Capillary.) Mercury and water 
are named as liquids in which the phenomena are most conveniently 
observed. They are observable in other parallel cases. 

Electrochemical Equivalent. The quantity of an element or 
compound liberated from or brought into combination, electrolytic- 
ally , by one coulomb of electricity . The electro-chemical equivalent 
of hydrogen is found by experiment to be .0000105 gram. That 
of any other substance is found by multiplying this weight by its 
chemical equivalent referred to hydrogen, which is its atomic or 
molecular weight divided by its valency. Thus the atomic weight 
of oxygen is 16, its valency is 2, its equivalent is 16 -f 2 = 8 ; its 
electro-chemical equivalent is equal to .0000105 X 8- .000840 
gram. 

Electrochemical Series. An arrangement of the elements in 
the order of their relative electrical affinities so that each element 
is electro-negative to all the elements following it, and electro-posi- 
tive to the elements preceding it. The usual series begins with 
oxygen as the most electro-negative and ends with potassium as the 
most electro-positive element. There is, of course, no reason why 
other series of compound radicals, such as sulphion (S O 4 ), etc., 
should not also be constructed. For each liquid acting on sub- 
stances a separate series of the substances acted on may be con- 
structed. Thus for dilute sulphuric acid the series beginning with 
the negatively charged or most attacked one is zinc, amalgamated 
or pure, cadmium, iron, tin, lead, aluminum, nickel, antimony, 
bismuth, copper, silver, platinum. In other liquids the series is 
altogether different. (See Electro-motive Series.) 

Electrochemistry. The branch of electricity or of chemistry 
treating of the relations between electric and chemical force in 
different compounds and reactions. (See Electrolysis — Electro* 
chemical series — Electro-chemical Equivalent .) 

Electroculture. The application of electricity to the cultivation 



210 STANDARD ELECTRICAL DICTIONARY. 

of plants. In one system wires are stretched or carried across the 
bed under the surface, and some are connected to one pole and 
others to the other pole of a galvanic battery of two or more ele- 
ments. In some experiments improved results have thus been 
obtained. 

Another branch refers to the action of the electric arc light on 
vegetation. This has an effect on vegetation varying in results. 

Electrode, (a) The terminal of an open electric circuit. 

(d) The terminals of the metallic or solid conductors of an electric 
circuit, immersed in an electrolytic solution. 

(c) The terminals between which a voltaic arc is formed, always 
in practice made of carbon, are termed electrodes. 

id) In electro-therapeutics many different electrodes are used 
whose names are generally descriptive of their shape, character, or 
uses to which they are to be applied. Such are aural electrodes for 
the ears, and many others. 

(e) The plates of a voltaic battery. 

Electrode, Indifferent. A term in electro-therapeutics. An 
electrode to which no therapeutic action is attributed but which 
merely provides a second contact with the body to complete the cir- 
cuit through the same. The other electrode is termed the thera- 
peutic electrode. 

Electrodes, Erb's Standards of. Proposed standard sizes for 
medical electrodes as follows : 

Diameter. 

inch 



Name. 


Diameter. 




Fine Klectrode, 
Small 

Medium " 
Large ' ' 
Very large " 


y 2 centimeter 

2 

7-5 " 
6x2 " 
16x8 


.2 
.8 

2.4X.8 
6.4x3.2 



Electrodes, Non=polarizable. In electro-therapeutics electrodes 
whose contact surface is virtually porous clay saturated with zinc 
chloride solution. The series terminate in amalgamated zinc ends, 
enclosed each in a glass tube, and closed with clay. Contact of 
metal with the tissues is thus avoided. 

Electrode, Therapeutic. A term in electro-therapeutics. An 
electrode applied to the body for the purpose of inducing therapeutic 
action,- or for giving the basis for an electric diagnosis of the 
case. The other electrode is applied to complete the circuit only ; 
it is termed the indifferent electrode. 

Electro=diagnosis. The study of the condition of a patient by 
the reactions which occur at the terminals or kathode and anode 



STANDARD ELECTRICAL DICTIONARY. 211 

of an electric circuit applied to the person. The reactions are 
divided into kathodic and anodic reactions. 

Electro=dynamic. adj. The opposite of electrostatic ; a qualifi- 
cation of phenomena due to current electricity. 

Synonym — Electro-kinetic. 

Electro=dynamic Attraction and Repulsion. The mutual 
attraction and repulsion exercised by currents of electricity upon 
each other. The theory of the cause is based upon stress of the 
luminiferous ether and upon the reaction of lines of force upon each 
other. For a resume of the theory see Induction, Electro-magnetic. 

Electro=dynamics. The laws of electricity in a state of motion ; 
the inter-reaction of electric currents. It is distinguished from 
electro-magnetic induction as the latter refers to the production of 
currents by induction. The general laws of electro-dynamics 
are stated under Induction, Electro-magnetic, q. v. 

Synonym — Electro-kinetics. 




Fig. 143. Diagram of Connections of Siemens' Electro-dynamometer. 



212 STANDARD ELECTRICAL DICTIONARY. 

Electro=dynamometer, Siemens'. An apparatus for meas- 
uring currents by the reaction between two coils, one fixed and one 
movable, through which the current to be measured passes. It is 
one of the oldest commercial ammeters or current measurers. It 
comprises a fixed coil of a number of convolutions and a movable 
coil often of only one convolution surrounding the other. The 
movable coil is suspended by a filament or thread from a spiral spring. 
The spring is the controlling factor. Connection is established 
through mercury cups so as to bring the two coils in series. In 
use the spring and filament are adjusted by turning a milled head 
to which they are connected until the coils are at right angles. 
Then the current is turned on and deflects the movable coil. 
The milled head is turned until the deflection is overcome. The 
angle through which the head is turned is proportional to the 
square of the current. The movable coil must in its position at 
right angles to the fixed one lie at right angles to the magnetic 
meridian. 

Thus in the diagram, Fig. 143 A B C D is the fixed coil ; E F 
G H is the movable coil ; ^ is the spiral spring attached at K to 
the movable coil. The arrows show the course of the current 
as it goes through the coils. 

Electrolier. A fixture for supporting electric lamps ; the 
analogue in electric lighting of the gasolier or gas chandelier. 
Often both are combined, the same fixture being piped and carrying 
gas burners, as well as being wired and carrying electric lamps. 

Electrolysis. The separation of a chemical compound into its 
constituent parts or elements by the action of the electric current. 
The compound may be decomposed into its elements, as water into 
hydrogen and oxygen, or into constituent radicals, as sodium sul- 
phate into sodium and and sulphion, which by secondary reactions 
at once give sodium hydrate and sulphuric acid. The decomposi- 
tion proceeds subject to the laws of electrolysis. (See Electrolysis, 
Laws of.) For decomposition to be produced there is for each 
compound a mininum electro-motive force or potential difference 
required. The current passes through the electrolyte or substance 
undergoing decomposition entirely by Electrolytic Conduction, q. v. 
in accordance with Grothuss' Hypothesis, q. v. The electrolyte 
therefore must be susceptible of diffusion and must be a fluid. 

The general theory holds that under the influence of a potential 
difference between electrodes immersed in an electrolyte, the mole- 
cules touching the electrodes are polarized, in the opposite sense 
for each electrode. If the potential difference is sufficient the 
molecules will give up one of their binary constituents to the 
electrode, and the other constituent will decompose the adjoining 
molecule, and that one being separated into the same two constit- 



STANDARD ELECTRICAL DICTIONARY. 



213 



uents will decompose its neighbor, and soon through the mass until 
the other electrode is reached. This one separates definitely the 
second binary constituent from the molecules touching it. 

Thus there is an exact balance preserved. Just as many mole- 
cules are decomposed at one electrode as at the other, and the 
exact chain of decomposition runs through the mass. Each com- 
pound electrolyzed develops a binary or two-fold composition, and 
gives up one constituent to one electrode and the other to the 
other. 




Fig. 144. 



Action of Molecules in a Solution Before and During 
Electrolysis. 



The cut shows the assumed polarization of an electrolyte. The 
upper row shows the molecules in irregular order before any 
potential difference has been produced, in other words, before the 
circuit is closed. The next row shows the first effects of closing 
the circuit, and also indicates the polarization of the mass, when 
the potential difference is insufficient for decomposition. The third 
row indicates the decomposition of a chain of molecules, one 
constituent separating at each pole. 

Electrolysis, Laws of. The following are the principal laws, 
originally discovered by Faraday, and sometimes called Faraday 's 
Laws of Electrolysis : 

I. Electrolysis cannot take place unless the electrolyte is a con- 
ductor. Conductor here means an electrolytic conductor, one that 
conducts by its own molecules traveling, and being decomposed. 
(See Grothuss^ Hypothesis.) 



214 STANDARD ELECTRICAL DICTIONARY. 

II. The energy of the electrolytic action of the current is the 
same wherever exercised in different parts of the circuit. 

III. The same quantity of electricity — that is the same current 
for the same period — decomposes chemically equivalent quantities 
of the bodies it decomposes, or the weights of elements separated in 
electrolytes by the same quantity of electricity (in coulombs or 
some equivalent unit) are to each other as their chemical equivalent. 

IV. The quantity of a body decomposed in a given time is pro- 
portional to the strength of the current. 

To these may be added the following : 

V. A definite and fixed electro-motive force is required for the 
decomposition of each compound, greater for some and less for 
others. Without sufficient electro-motive force expended on the 
molecule no decomposition will take place. (See Current, Convective. ) 

Electrolyte. A body susceptible of decomposition by the elec- 
tric current, and capable of electrolytic conduction. It must be a 
fluid body and therefore capable of diffusion, and composite in com- 
position. An elemental body cannot be an electrolyte. 

Electrolytic Analysis, Chemical analysis by electrolysis. The 
quantitative separation of a number of metals can be very effect- 
ively executed. Thus, suppose that a solution of copper sulphate 
was to be analyzed. A measured portion of the solution would be 
introduced into a weighed platinum vessel. The vessel would be 
connected to the zinc plate terminal of a battery. From the other ter- 
minal of the battery a wire would be brought and would terminate 
in a plate of platinum. This would be immersed in the solution in 
the vessel. As the current would pass the copper sulphate would be 
decomposed and eventually all the copper would be deposited in a 
firm coating on the platinum. The next operations would be to 
wash the metal with distilled water, and eventually with alcohol, to 
dry and to weigh the dish with the adherent copper. On subtracting 
the weight of the dish alone from the weight of the dish and copper, 
the weight of the metallic copper in the solution would be obtained. 

In similar ways many other determinations are effected. The 
processes of analysis include solution of the ores or other substances 
to be analyzed and their conversion into proper form for elec- 
trolysis. Copper as just described can be precipitated from the solu- 
tion of its sulphate. For iron and many other metals solutions of 
their double alkaline oxalates are especially available forms for 
analysis. 

The entire subject has been worked out in considerable detail by 
Classen, to whose works reference should be made for details of 
processes. 

Electrolytic Convection. It is sometimes observed that a single 



STANDARD ELECTRICAL DICTIONARY. 215 

cell of Daniell battery, for instance, or other source of electric 
current establishing too low a potential difference for the decomposi- 
tion of water seems to produce a feeble but continuous decomposi- 
tion. This is very unsatisfactorily accounted for by the hydrogen 
as liberated combining with dissolved oxygen. (Ganot.) The 
whole matter is obscure. (See Current, Convection.) 

Electrolytic Conduction. Conduction by the travel of atoms 
or radicals from molecule to molecule of a substance with eventual 
setting free at the electrodes of the atoms or radicals as elementary 
molecules or constituent radicals. A substance to be capable of 
acting as an electrolytic conductor must be capable of diffusion, and 
must also have electrolytic conductivity. Such a body is called an 
electrolyte. (See Grothuss' Hypothesis — Electrolysis — Electrolysis, 
Laws of— Electro-chemical Equivalent.) 

Electro=magnet. A mass, in practice always of iron, around 
which an electric circuit is carried, insulated from the iron. When 
a current is passed through the circuit the iron presents the charac- 
teristics of a magnet. (See Magnetism, Ampere } s Theory of— 
Solenoid — Lines of Force.) In general terms the action of a circular 
current is to establish lines of force that run through the axis of the 
circuit approximately parallel thereto, and curving out of and over 
the circuit, return into themselves outside of the circuit. If a mass 
of iron is inserted in the axis or elsewhere near such current, it 
multiplies within itself the lines of force, q. v. (See also Magnetic 
Permeability — Permeance — Magnetic Induction, Coefficient of— 
Mag?ietic Susceptibility — Mag7ietization, Coefficient of Induced.) 
These lines of force make it a magnet. On their direction, which 
again depends on the direction of the magnetizing current, depends 
the polarity of the iron. The strength of an electro-magnet, below 
saturation of the core (see Magnetic Saturation), is proportional 
nearly to the ampere-turns, q. v. More turns for the same current 
or more current for the same turns increase its strength. 

In the cut is shown the general relation of current, coils, core 
and line of force. Assume that the magnet is looked at endwise, the 
observer facing one of the poles ; then if the current goes around 
the core in the direction opposite to that of the hands of a clock, 
such pole will be the north pole. If the current is in the direction 
of the hands of a clock the pole facing the observer will be the south 
pole. The whole relation is exactly that of the theoretical Amp£rian 
currents, already explained. The direction and course of the lines 
of force created are shown in the cut. 

The shapes of electro-magnets vary greatly. The cuts show several 
forms of electro-magnets. A more usual form is the horseshoe 
or double limb magnet, consisting generally of two straight cores, 
wound with wire and connected and held parallel to each other by 
a bar across one end, which bar is called the yoke. 



2l6 



STANDARD ELECTRICAL DICTIONARY. 



In winding such a magnet the wire coils must conform, as regards 
direction of the current in them to the rule for polarity already 




Fig. x* 5 . 



Diagram of an Electro-magnet Showing Relation of Current 
and Winding to its Polarity and Lines of Force. 



cited. If both poles are north or both are south poles, then the 
magnet cannot be termed a horseshoe magnet, but is merely an 
anomalous magnet. In the field mag- 
nets of dynamos the most varied types 
of electro-magnets have been used. 
Consequent poles are often produced in 
them by the direction of the windings 
and connections. 

To obtain the most powerful magnet 
the iron core should be as short and 
thick as possible in order to diminish 
the reluctance of the magnetic circuit. 
To obtain a greater range of action a 
long thin shape is better, although it 
involves waste of energy in its excita- 
tion. 

Electro=magnet, Annular. An 
electro-magnet consisting of a cylin- 
der with a circular groove cut in its 
face, in which groove a coil of insulated 
wire is placed. On the passage of a 
current the iron becomes polarized 
and attracts an armature towards or 
against its grooved face. The cut shows 
the construction of an experimental 
one. It is in practice applied to 
brakes and clutches. In the cut of the 




Fig. 146. 



STANDARD ELECTRICAL DICTIONARY. 



217 



electro-magnetic brake (see Brake, Electro-magnetic) , C is the 
annular magnet receiving its current through the wires, and 
pressed when braking action is required against the face of the 
moving wheel. The same arrange- 
ment, it can be seen, may apply to a 
clutch. 

EIectro=magnet, Bar. A straight 
bar of iron surrounded with a mag- 
netizing coil of wire. Bar electro- 
magnets are not much used, the horse- 
shoe type being by far the more usual. 

Fig. 147. Bar Electro-magnet. 

Electro=magnet, Club=foot. An electro-magnet, one of whose 
legs only is wound with wire, the other being bare. 




1 e 


i^^^*^ - """" 






1 " *^ hi ' ^= 
























i—3 i 




V 









y|o l 






- 
J 
























W- 



Fig. 148. Club-foot Electro-magnets with Hinged Armatures. 

Electro=magnet, Hinged. An electro-magnet whose limbs are 
hinged at the yoke. On excitation by a current the poles tend to 
approach each other. 

Electro=magnetic Attrac= 
tionancLRepuIsion. The attrac- 
tion and repulsion due to electro- 
magnetic lines of force, which 
lines always tend to take as short 
a course as possible and also seek 
the medium of the highest per- 
meance. This causes them to 
concentrate in iron and steel or 
other paramagnetic substance and to draw them towards a magnet 
by shortening the lines of force connecting the two. It is exactly 
the same attraction as that of the permanent magnet for its arma- 
ture, Ampere's theory bringing the latter under the same title. In 
the case of two magnets like poles repel and unlike attract. In 




Fig. 149. Electro-magnet, Hinged. 



218 STANDARD Bl/KCTRICAIv DICTIONARY. 

the case of simple currents, those in the same direction attract 
and those in opposite directions repel each other. This refers to 
constant current reactions. Thus the attraction of unlike poles of 
two magnets is, by the Amperian theory, the attraction of two sets 
of currents of similar direction, as is evident from the diagram. 
The repulsion of like poles is the repulsion of unlike currents and 
the same applies to solenoids, q. v. (See Magnetism and do. 
Ampere's Theory of— Induction , Electro-dynamic — Electro-mag- 
netic Induction . ) 

Electro=magnetic Control. Control of a magnet, iron arma- 
ture, or magnetic needle in a galvanometer, ammeter, voltmeter 
or similar instrument by an electro-magnetic field, the restitutive 
force being derived from an electro-magnet. The restitutive force 
is the force tending to bring the index to zero. 

Electro=magnetic Field of Force. A field of electro-magnetic 
lines of force, q. v., established through the agency of an electric 
current. A wire carrying a current is surrounded by circular 
concentric lines of force which have the axis of the wire as the 
locus of their centres. Blectro-magnets produce lines of force 
identical with those produced by permanent magnets. (See Field 
of Force — Magnetic Field of Force — Controlling Field — Deflect- 
ing Field.) 

Electro=magnetic Induction. When two currents of unlike 
direction are brought towards each other, against their natural 
repulsive tendency work is done, and the consequent energy takes 
the form of a temporary increase in both currents. When with- 
drawn, in compliance with the natural tendency of repulsion, the 
currents are diminished in intensity, because energy is not 
expended on the withdrawal, but the withdrawal is at the expense 
of the energy of the system. The variations thus temporarily 
produced in the currents are examples of electro-magnetic induc- 
tion. The currents have only the duration in each case of the 
motion of the circuits. One circuit is considered as carrying the 
inducer current and is termed the primary circuit and its current 
the primary current, the others are termed the secondary circuit and 
current respectively. We may assume a secondary circuit in which 
there is no current. It is probable that there is always an infin- 
itely small current at least, in every closed circuit. Then an 
approach of the circuits will induce in the secondary an instantane- 
ous current in the reverse direction. On separating the two cir- 
cuits a temporary current in the same direction is produced in the 
secondary. 

A current is surrounded by lines of force. The approach of two 
circuits, one active, involves a change in the lines of force about 
the secondary circuit. Iyines of force and current are so intimately 



STANDARD ELECTRICAL DICTIONARY. 219 

connected that a change in one compels a change in the other. 
Therefore the induced current in the secondary may be attributed 
to the change in the field of force in which it lies, a field main- 
tained by the primary circuit and current. Any change in a field 
of force induces a current or change of current in any closed cir- 
cuit in such field, lasting as long as the change is taking place. 
The new current will be of such direction as to oppose the change. 
(See Lenz's Law.) 

The action as referred to lines of force may be figured as the 
cutting of such lines by the secondary circuit, and such cutting 
may be brought about by moving the secondary in the field. (See 
Lines of Force — Field of Force.} The cutting of io 8 lines of force 
per second by a closed circuit induces an electro-motive force of 
one volt. (See Induction, Mutual, Coefficient of) 

Electromagnet, Iron Clad. A magnet whose coil and core are 
encased in a iron jacket, generally connected to one end of the 
core. This gives at one end two poles, one tubular, the other solid, 
and concentric with each other. It is sometimes called a tubular 
magnet. 

Electro=magnet, One Coil. An electro-magnet excited by one 
coil. In some dynamos the field magnets are of this construction, 
a single coil, situated about midway between the poles, producing 
the excitation. 

Electro=magnetic Leakage. The leakage of lines of force in an 
electro-magnet ; the same as magnetic leakage. (See Magnetic 
Leakage.) 

Electro=magnetic Lines of Force. The lines of force produced 
in an electro-magnetic field. They are identical with Magnetic 
Lines of Force, q. v. (See also Field of Force — Line of Force.) 

Electro=magnetic Stress. The stress in an electro-magnetic 
field of force, showing itself in the polarization of light passing 
through a transparent medium in such a field. (See Magnetic 
Rotary Polarization . ) 

Electro=magnetic Theory of Light. This theory is due to J. 
Clark Maxwell, and the recent Hertz experiments have gone far 
to prove it. It holds that the phenomena of light are due to ether 
waves, identical in general factors with those produced by electro- 
magnetic induction of alternating currents acting on the ether. In 
a non-conductor any disturbance sets an ether wave in motion 
owing to its restitutive force ; electricity does not travel through 
such a medium, but can create ether waves in it. Therefore a non- 
conductor of electricity is permeable to waves of ether or should 
transmit light, or should be transparent. A conductor on the other 
hand transmits electrical disturbances because it has no restitutive 



220 STANDARD ELECTRICAL DICTIONARY. 

force and cannot support an ether wave. Hence a conductor 
should not transmit light, or should be opaque. With few excep- 
tions dielectrics or non-conductors are transparent, and conductors 
are opaque. 

Again, the relation^ between the electrostatic and electro-magnet 
units of quantity is expressed by i : 30,000,000,000 ; the latter figure 
in centimeters gives approximately the velocity of light. The 
electro-magnetic unit depending on electricity in motion should 
have this precise relation if an electro-magnetic disturbance was 
propagated with the velocity of light. If an electrically charged 
body were whirled around a magnetic needle with the velocity of 
light, it should act in the same way as a current circulating around 
it. This effect to some extent has been shown experimentally by 
Rowland. 

A consequence of these conclusions is (Maxwell) that the specific 
inductive capacity of a non-conductor or dielectric should be equal 
to the square of its index of refraction for waves of infinite length. 
This is true for some substances — sulphur, turpentine, petroleum 
and benzole. In others the specific inductive capacity is too high, 
e. g., vegetable and animal oils, glass, Iceland spar, fluor spar, 
and quartz. 

Electro=magnetic Unit of Energy. A rate of transference of 
energy equal to ten meg-ergs per second. 

Electro=magnetism. The branch of electrical science treating 
of the magnetic relations of a field of force produced by a current, 
of the reactions of electro-magnetic lines of force, of the electro- 
magnetic field of force, of the susceptibility, permeability, and 
reluctance of dia- and paramagnetic substances, and of electro- 
magnets in general. 

Electro=magnet, Long Range. An electro-magnet so constructed 
with extended pole pieces or otherwise, as to attract its armature 
with reasonably constant force over a considerable distance. The 
coil and plunger, q. v. , mechanisms illustrate one method of getting 
an extended range of action. When a true electro-magnet is used, 
one with an iron core, only a very limited range is attainable at 
the best. (See Electro-magnet, Stopped Coil — do. Plunger.) 

Electro=magnet, Plunger. An electro-magnet with hollow 
coils, into which the armature enters as a plunger. To make it a 
true electro-magnet it must have either a yoke, incomplete core, 
or some polarized mass of iron. 

Electro=magnet, Polarized. An electro-magnet consisting 
of a polarized or permanently magnetized core wound with mag- 
netizing coils, or with such coils on soft iron cores mounted on its 



STANDARD ELECTRICAL DICTIONARY. 



ends. The coils may be wound and connected so as to co-operate 

with or work against the permanent magnet on which it is 

mounted. In Hughes' magnet showm in 

the cut it is mounted in opposition, so that 

an exceedingly feeble current will act to , 

displace the armature, a, which is pulled 

away from the magnet by a spring, s. 

Electro=magnets, Interlocking. 

Electro-magnets so arranged that their 
armatures interlock. Thus tw T o magnets, 
A A and B B, may be placed with their 
armatures, M and N y at right angles and 
both normally pulled away from the poles. 
When the armature M is attracted a catch 
on its end is retained by a hole in the „. 
end of the other armature N, and when** *$. ^7™"™*° 
the latter armature N is attracted by its 

magnet the armature M is released. In the mechanism shown 
in the cut the movements of the wheel R are controlled. Nor- 
mally it is held motionless by the catch upon the bottom of the 





Fig. 151. Interlocking Electro-magnets.' 

armature M, coming against the tooth projecting from its periph- 
ery. A momentary current through the coils of the magnet A 
A releases it, by attracting M } which is caught and retained 
by N, and leaves it free to rotate. A momentary current 
through the coils of the magnet B B again releases M, which drops 
down and engages the tooth upon R and arrests its motion. 

Electro-magnet, Stopped Coil. An electro-magnet consisting 
of a tubular coil, in which a short fixed core is contained, stopping 
up the aperture to a certain distance, while the armature is a 



222 STANDARD ELECTRICAL DICTIONARY. 

plunger entering the aperture. This gives a longer range of action 
than usual. 

Electro=magnet, Surgical. An electro-magnet, generally of 
straight or bar form, fitted with different shaped pole pieces, used 
for the extraction of fragments of iron or steel from the eyes. 
Some very curious cases of successful operations on the eyes of 
workmen, into whose eyes fragments of steel or iron had pene- 
trated, are on record. 

Electromedical Baths. A bath for the person provided with 
connections and electrodes for causing a current of electricity of 
any desired type to pass through the body of the bather. Like all 
electro-therapeutical treatment, it should be administered under 
the direction of a physician only. 

Electro=metallurgy. (a) In the reduction of ores the electric 
current has been proposed but never extensively used, except in 
the reduction of aluminum and its alloys. (See Reduction of Ores > 
Electric) 

(b) Electro-plating and deposition of metal from solutions is 
another branch. (See Electroplating and Electrotyping.) 

(c) The concentration of iron ores by magnetic attraction may 
come under this head. (See Magnetic Concentration of Ores.) 

Electrometer. An instrument for use in the measurement of 
potential difference, by the attraction or repulsion of statically 
charged bodies. They are distinguished from galvanometers as the 
latter are really current measurers, even if wound for use as volt- 
meters, depending for their action upon the action of the current 
circulating in their coils. 

Electrometer, Absolute. An electrometer designed to give 
directly the value of a charge in absolute units. In one form a 
plate, ad, of conducting surface is supported or poised horizontally 
below a second larger plate C, also of conducting surface. The poised 
plate is surrounded by a detached guard ring— an annular or perforated 
plate, r g r f g / — exactly level and even with it as regards the upper 
surface. The inner plate is carried by a delicate balance. In use 
C is connected to one of the conductors and the lower plate to 
earth or to the other. The attraction between them is determined 
by weighing. By calculation the results can be made absolute, as 
they depend on actual size of the plates and their distance, outside 
of the potential difference of which of course nothing can be said. 
If S is the area of the disc, d the distance of the plates, V — V 1 the 
difference of their potential, which is to be measured, and F the 
force required to balance their attraction, we have : 

(V— V 1 ) 2 s 
F = .(i) 

STtd 2 



STANDARD ELECTRICAL DICTIONARY. 
If V = O this reduces to 



223 



V 2 S 



8tt d 2 
^ttF 



V: 



(3) 



v S 

As F is expressed as a weight, and S and a as measures of area 
and length, this gives a means of directly obtaining potential values 
in absolute measure. (See I dio static Method — Heterostatic Method. ) 

Synonyms— Attracted Disc Electrometer — Weight Electrometer. 




Fig. 152. Section of Base of Portable Electrometer. 

In some forms the movable disc is above the other, and supported 
at the end of a balance beam. In others a spring support, arranged 
so as to enable the attraction to. be determined in weight units, 
is adopted. The cuts, Figs. 152 and 154, show one of the latter type, 
the portable electrometer. The disc portion is contained within a 



T a 


b r' 




| 





3' 



Figf« I 53- Diagram Illustrating Theory of Absolute Electrometer. 

cylindrical vessel. Referring to Fig. 152 g is the stationary disc, 
charged through the wire connection r;f'ts the movable disc, car- 
ried by a balance beam poised at i on a horizontal and transverse 
stretched platinum wire, acting as a torsional spring. The position 
of the end k of the balance beam shows when the disc f is in the 
plane of the guard ring h h. The end k is forked horizontally and 
a horizontal sighting wire or hair is fastened across the opening of 



224 



STANDARD ELECTRICAL DICTIONARY. 



the fork. When the hair is midway between two dots on a vertical 
scale the lever is in the sighted position, as it is called, and the disc 
is in the plane of the guard ring. 




Fig. 154. Portable Electrometer. 

The general construction is seen in Fig. 154. There the fixed disc 
D is carried by insulating stem g x . The charging electrode is sup- 
ported by an insulating stem g 2 , and without contact with the box 
passes out of its cover through a guard tube E, with cover, some- 
times called umbrella, V. The umbrella is to protect the apparatus 
from air currents. At m is the sighting lens. H is a lead box 
packed with pumice stone, moistened with oil of vitriol or concen- 
trated sulphuric acid, to preserve the atmosphere dry. Before use 
the acid is boiled with some ammonium sulphate to expel any 
corrosive nitrogen oxides, which might corrode the brass. 

In use the upper disc is charged by its insulated electrode within 
the tube E ; the movable disc is charged if desired directly through 
the case of the instrument. The upper disc is screwed up or down 
by the micrometer head M, until the sighted position is reached. 
The readings of the micrometer on the top of the case give the data 
for calculation. 

Electrometer, Capillary. An electrometer for measuring 
potential difference by capillary action, which latter is affected by 



STANDARD ELECTRICAL DICTIONARY. 



225 



electrostatic excitement. A tube A contains mercury ; its end 
drawn out to a fine aperture dips into a vessel B which contains 
dilute sulphuric acid with mercury under it, as shown. Wires 




Fig. 155. Lippman's Capillary Electrometer. 

running from the binding-posts a and b connect one with the mer- 
cury in A, the other with that in B. The upper end of the tube A 
connects with a thick rubber mercury reservoir T, and manometer 
H. The surface tension of the mercury-acid film at the lower end 
of the tube A keeps all in equilibrium. If now a potential difference 
is established between a and b> as by connecting a battery thereto, 
the surface tension is increased and the mercury rises in the tube 
B. By screwing down the compressing clamp E, the mercury is 
brought back to its original position. The microscope M is used to 
determine this position with accuracy. The change in reading of 
the manometer gives the relation of change of surface tension and 
therefore of potential. Each electrometer needs special graduation 
or calibration, but is exceedingly sensitive and accurate. It cannot 
be used for greater potential differences than .6 volt, but can 
measure .0006 volt. Its electrostatic capacity is so small that it 
can indicate rapid changes. Another form indicates potential 
difference by the movement of a drop of sulphuric acid in a hori- 
zontal glass tube, otherwise filled with mercury, and whose ends 
lead into two mercury cups or reservoirs. The pair of electrodes to 
be tested are connected to the mercury vessels. The drop moves 
towards the negative pole, and its movement for small potential 
differences (less than one volt) is proportional to the electro-motive 
force or potential difference. 



226 



STANDARD ELECTRICAL DICTIONARY. 



Electrometer Gauge. An absolute electrometer (see Electro- 
meter \ Absolute) forming an attachment to a Thomson quadrant 
electrometer. It is used to test the potential of the flat needle 
connected with the inner surface of the Leyden jar condenser of 
the apparatus. This it does by measuring the attraction between 
itself and an attracting disc, the latter connected by a conductor 
with the interior of the jar. 

Electrometer, Lane's. A Leyden jar with mounted discharger, 
so that when charged to a certain point it discharges itself. It is 
connected with one coating of any jar whose charge is to be meas- 
ured, which jar is then charged by the other coating. As the jar 
under trial becomes charged to a certain point the electrometer jar 
discharges itself, and the number of discharges is the measure of 
the charge of the other jar. It is really a unit jar, q. v. 

Electrometer, Quadrant, (a) Sir William Thomson's electro- 
meter, a simple form of which is shown in the cut, consists of 
four quadrants of metal placed horizontally ; above these a broad 
flat aluminum needle hangs by a very fine wire, acting as torsional 
suspension. The quadrants are insulated from each other, but the 





Fig. 156. Thomson's Quad- 
rant Electrometer. 



Fig. 157. Henley's Quadrant 
Electroscope. 



opposite ones connect with each other by wires. The apparatus 
is adjusted so that, when the quadrants are in an unexcited con- 
dition the needle is at rest over one of the diametrical divisions 
between quadrants. The needle by its suspension wire is in com- 
munication with the interior of a lyeyden jar which is charged. 
The whole is covered with a glass shade, and the air within is kept 
dry by a dish of concentrated sulphuric acid so that the jar retains its 
charge for a long time and keeps the needle at approximately a 



STANDARD ELECTRICAL DICTIONARY. 227 

constant potential. If now two pairs of quadrants are excited with 
opposite electricities, as when connected with the opposite poles of 
an insulated galvanic cell, the needle is repelled by one pair and 
attracted by the other, and therefore rotates through an arc of greater 
or less extent. A small concave mirror is attached above the 
needle and its image is reflected on a graduated screen. This makes 
the smallest movement visible. Sometimes the quadrants are double, 
forming almost a complete box, within which the needle moves. 

(b) Henley's quadrant electrometer is for use on the prime con- 
ductor of an electric machine, for roughly indicating the relative 
potential thereof. It consists of a wooden standard attached per- 
pendicularly to the conductor. Near one end is attached a semi- 
circular or quadrant arc of a circle graduated into degrees or angu- 
lar divisions. An index, consisting of a straw with a pith-bell 
attached to its end hangs from the center of curvature of the arc. 
When the prime conductor is charged the index moves up over 
the scale and its extent of motion indicates the potential relatively. 

When the " quadrant electrometer" is spoken of it may always 
be assumed that Sir William Thomson's instrument is alluded to. 
Henley's instrument is properly termed a quadrant electroscope. 
(See Electroscope.) 

Electro=motive Force. The cause which produces currents of 
electricity. In general it can be expressed in difference of poten- 
tials, although the term electro-motive force should be restricted to 
potential difference causing a currrent. It is often a sustained 
charging of the generator terminals whence the current is taken. 
Its dimensions are work done -f- the quantity of electricity involved, 
or ML 2 /T 2 ^ M* L*= M* L*/T 2 . 

The practical unit of electro-motive force is the volt, q. v. It is 
often expressed in abbreviated form, as E. M. D. P., or simply 
as D. P. , i.e., potential difference. 

Electro-motive force and potential difference are in many cases 
virtually identical, and distinctions drawn between them vary with 
different authors. If we consider a closed electric circuit carrying 
a current, a definite electro-motive force determined by Ohm's law 
from the resistance and current obtains in it. But if we attempt to 
define potential difference as proper to the circuit we may quite 
■^ail. Potential difference in a circuit is the difference in potential 
between defined points of such circuit. But no points in a closed 
circuit can be found which differ in potential by an amount equal 
to the entire electro- motive force of the circuit. Potential differ- 
ence is properly the measure of electro-motive force expended on 
the portion of a circuit betw r een any given points. Electro-motive 
force of an entire circuit, as it is measured, as it were, between two con- 
secutive points but around the long portion of the circuit, is not con- 



228 STANDARD ELECTRICAL DICTIONARY. 

ceivable as merely potential difference. Taking the circle divided 
into degrees as an analogy, the electro-motive force of the entire cir- 
cuit might be expressed as 360 , which are the degrees intervening 
between two consecutive points, measured the long way around 
the circle. But the potential difference between the same two 
points would be only i°, for it would be measured by the nearest 
path. 

Electro=motive Force, Counter, A current going through a 
circuit often has not only true or ohmic resistance to overcome, but 
meets an opposing E. M. F. This is termed counter-electro-motive 
force. It is often treated in calculations as resistance, and is 
termed spurious resistance. It may be a part of the impedance of 
a circuit. 

In a primary battery hydrogen accumulating on the negative 
plate develops counter E. M. F. In the voltaic arc the differential 
heating of the two carbons does the same. The storage battery is 
changed by a current passing in the opposite direction to its own 
natural current ; the polarity of such a battery is counter E. M. F. 

EIectro=motive Force, Unit. Unit electro-motive force is that 
which is created in a conductor moving through a magnetic field 
at such a rate as to cut one unit line of force per second. It is that 
which must be maintained in a circuit of unit resistance to main- 
tain a current of unit quantity therein. It is that which must be 
maintained between the ends of a conductor in order that unit 
current may do unit work in a second. 

Electro=motive Intensity. The force acting upon a unit charge 
of electricity. The mean force is equal to the difference of poten- 
tial between two points within the field situated one centimeter 
apart, such distance being measured along the lines of force. The 
term is due to J. Clerk Maxwell. 

Electro=motive Series. Arrangement of the metals and carbon 
in series with the most electro-positive at one end, and electro- 
negative at the other end. The following are examples for differ- 
ent exciting liquids : 



ilute Sulphuric 


Dilute Hydrochloric 


Caustic 


Potassium 


Acid 


Acid. 


Potash. 


Sulphide. 


Zinc 


Zinc 


Zinc 


Zinc 


Cadmium 


Cadmium 


Tin 


Copper 


Tin 


Tin 


Cadmium 


Cadmium 


I^e ad 


L,ead 


Antimony 


Tin 


Iron 


Iron 


I,ead 


Silver 


Nickel 


Copper 


Bismuth 


Antimony 


Bismuth 


Bismuth 


Iron 


I^ead 


Antimony 


Nickel 


Copper 


Bismuth 


Copper 


Silver 


Nickel 


Nickel 



STANDARD ELECTRICAL DICTIONARY. 



229 



Dilute Sulphuric 
Acid. 

Silver 
Gold 
Platinum 
Carbon 



Dilute Hydrochloric 
Acid. 

Antimony 



Caustic 
Potash. 

Silver 



Potassium 
Sulphide. 

Iron 



In each series the upper metal is the positive, dissolved or 
attacked element. (See Contact Series — Electro-chemical Series.) 

Electro=motograph. An invention of Thomas A. Edison. A 
cylinder of chalk, moistened with solution of caustic soda, is 
mounted so as to be rotated by a handle. A diaphragm has an arm 
connected to its center. This arm is pressed against the surface of 
the cylinder by a spring. When the cylinder is rotated, a constant 
tension is exerted on the diaphragm. If a current is passed through 
the junction of arm and cylinder the electrolytic action alters the 
friction so as to change the stress upon the diaphragm. 

If the current producing this effect is of the type produced by 
the human voice through a microphone the successive variations 
in strain upon the diaphragm will cause it to emit articulate 
sounds. These are produced directly by the movement of the 
cylinder, the electrolytic action being rather the regulating por- 
tion of the operation. Hence very 
loud sounds can be produced by it. 
This has given it the name of the 
loud-speaking telephone. 

The same principle may be applied 
in other ways. But the practical ap- 
plication of the motograph is in the 
telephone described. 

Electro=motor. This term is some- 
times applied to a current generator, 
such as a voltaic battery. 

Electro=muscuIar Excitation. 

A term in medical electricity indicat- 
ing the excitation of muscle as the 
effect of electric currents of any kind. 

EIectro=negative. adj. Apper- 
taining to negative electrification ; 
thus of the elements oxygen is the 
most electro-negative, because if 
separated by electrolytic action from any combination, it will be 
charged with negative electricity. 

Electro = optics. The branch of natural science treating of the 
relations between light and electricity. Both are supposed to be 




Electro-motograph 
Telephone 



230 



STANDARD ELECTRICAL DICTIONARY. 



phenomena of or due to the luminiferous ether. To it may be 
referred the following : (a) Electro-magnetic Stress and Magnetic 
Rotary Polarization ; \b) Dielectric Strain ; all of which may 
be referred to in this book ; (c) Change in the resistance of a con- 
ductor by changes in light to which it is exposed (see Selenium) ; 
(d) The relation of the index of refraction of a dielectric to the 
dielectric constant (see Electro-magnetic Theory of Light).; (e) The 
identity (approximate) of the velocity of light in centimeters and 
the relative values of the electrostatic and electro-magnet units 
of intensity, the latter being 30,000,000,000 times greater than the 
former, while the velocity of light is 30,000,000,000 centimeters 
per second. 

Electrophone Action. The action of an electrophorous ; util- 
ized in influence machines. (See Electrophorous.) 

Electrophorous. An apparatus for the production of electric 
charges of high potential by electrostatic induction , q. v. It con- 
sists of a disc of insulating material i?, such as resin or gutta percha, 
which is held in a shallow metal-lined box or form. The disc may 
be half an inch thick and a foot or more in diameter, or may be 
much smaller and thinner. A metal disc A, smaller in diameter is 
provided with an insulating handle which may be of glass, or simply 
silk suspension strings. To use it the disc B is excited by friction 
with a cat-skin or other suitable substance. The metallic disc is 
then placed on the cake of resin exactly in its centre, so that the 




Fig. 159. Electrophorous. 

latter disc or cake projects on all sides. Owing to roughness there 
is little real electric contact between the metal and dielectric. On 
touching the metal disc a quantity of negative electricity escapes 
to the earth. On raising it from the cake it comes off excited 



STANDARD ELECTRICAL DICTIONARY. 231 

positively, and gives a spark and is discharged. It can be replaced, 
touched, removed and another spark can be taken from it, and so 
on as long as the cake stays charged. 

The successive discharges represent electrical energy expended. 
This is derived from the muscular energy expended by the oper- 
ator in separating the two discs when oppositely excited. As 
generally used it is therefore an apparatus for converting muscular 
or mechanical energy into electric energy. 

Electro=physiology. The science of the electric phenomena 
of the animal system. It may also be extended to include plants. 
The great discovery of Galvani with the frog's body fell into this 
branch of science. The electric fishes, gymnotus, etc., present 
intense phenomena in the same. 

Electroplating. The deposition by electrolysis of a coating of 
metal upon a conducting surface. The simplest system makes the 
object to be plated the negative electrode or plate in a galvanic 
couple. Thus a spoon or other object may be connected by a wire 
to a plate of zinc. A porous cup is placed inside a battery jar. The 
spoon is placed in the porous cup and the zinc outside it. A solu- 
tion of copper sulphate is placed in the porous cup, and water with 
a little sodium or zinc sulphate dissolved in it, outside. A current 
starts through the couple, and copper is deposited on the spoon. 

A less primitive w T ay is to use a separate battery as the source of 
current ; to connect to the positive plate by a wire the object to be 
plated, and a plate of copper, silver, nickel or other metal to the 
| other pole of the battery. On immersing both object and plate 
(anode) in a bath of proper solution the object will become plated. 

I In general the anode is of the same material as the metal to fae 
deposited, and dissolving keeps up the strength of the bath. There 
are a great many points of technicality involved which cannot be 
given here. The surface of the immersed object must be conduc- 
tive. If not a fine wire network stretched over it will gradually 
fill up in the bath and give a matrix. More generally the surface 
is made conductive by being brushed over with plumbago. This 
may be followed by a dusting of iron dust, followed by immersion 
in solution ol copper sulphate. This has the effect of depositing 
metallic copper over the surface as a starter for the final coat. 

Attention must be paid to the perfect cleanliness of the objects, 
to the condition of the bath, purity of anodes and current density. 

Voltaic batteries are largely used for the current as well as special 
low resistance dynamo's. Thermo-electric batteries are also used to 
some extent but not generally. 

Electro=pneumatic Signals. Signals, such as railroad signals 
or semaphores, moved by compressed air, which is controlled by 



232 STANDARD ELECTRICAL DICTIONARY. 

valves operated by electricity. The House telegraph, which was 
worked by air controlled by electricity, might come under this 
term, but it is always understood as applied to railroad signals, or 
their equivalent. 

Electropoion Fluid. An acid depolarizing solution for use in 
zinc-carbon couples, such as the Grenet battery. The following are 
formulae for its preparation : (a) Dissolve one pound of potassium 
bichromate in ten pounds of water, to which two and one-half 
pounds of concentrated sulphuric acid have been gradually added. 
The better way is to use powdered potassium bichromate, add it to 
the water first, and then gradually add the sulphuric acid with con- 
stant stirring, (b) To three pints of water add five fluid ounces of 
concentrated sulphuric acid ; add six ounces pulverized potassium 
bichromate, (c) Mix one gallon concentrated sulphuric acid and 
three gallons of water. In a separate vessel dissolve six pounds 
potassium bichromate in two gallons of boiling water. Mix the 
two. 

The last is the best formula. Always use electropoion fluid cold. 
(See Trouve's Solution — Poggendorjfs Solution — Kakogey's 
Solution — Tissandrier' s Solution — Chutaux^s Solution,) I 

Electro=positive. adj. Appertaining to positive electrification ; 
thus potassium is the most electro-positive of the elements. (See 
Electro-negative. ) 

Electro=puncture. The introduction into the system of a 
platinum point or needle, insulated with vulcanite, except near its 
point, and connected as the anode of a galvanic battery. The 
kathode is a metal one, covered with a wet sponge and applied on 
the surface near the place of puncture. It is used for treatment of 
aneurisms or diseased growths, and also for removal of hair by 
electrolysis. (See Hair, Removal of by Electrolysis,) 

Synonym- — Galvano-puncture. 

Electro-receptive, adj. A term applied to any device or appara- 
tus designed to receive and absorb electric energy. A motor is an 
example of an electro-receptive mechanism. 

Electroscope. An apparatus for indicating the presence of an 
electric charge, and also for determining the sign, or whether the 
charge is positive or negative. The simplest form consists of a 
thread doubled at its centre and hung therefrom. On being 
charged, or on being connected to a charged body the threads 
diverge. A pair of pith balls may be suspended in a similar way, 
or a couple of strips of gold leaf within a flask (the gold leaf 
electroscope). To use an electroscope to determine the sign of the 
charge it is first slightly charged. The body to be tested is then 
applied to the point of suspension, or other charging point. If at 



STANDARD ELECTRICAL DICTIONARY. 



233 



once further repelled the charge of the body is of the same sign as 
the slight charge first imparted to the electroscope leaves ; the 
leaves as they become more excited will at once diverge more. If 
of different sign they will at first approach as their charge is neu- 
tralized and will afterwards diverge. 

The gold-leaf electroscope is generally enclosed in a glass bell 
jar or flask. Sometimes a pair of posts rise, one on each side, to 
supply points of induction from the earth to intensify the action. 
(See Electrometer , Quadra?it — Electroscope, Gold leaf, and others.) 

Electroscope, Bennett's. A gold-leaf electroscope, the sus- 
pended leaves of which are contained in a glass shade or vessel of dry 
air. On the inside of the glass shade are two strips of gold leaf, 
which rise from the lower edge a short distance, being pasted to 
the glass, and connected to the ground. These act by induction to 
increase the sensitiveness of the instruments. 

Electroscope, Bohenberger's. A condensing electroscope 
(see Electroscope, Condensing) with a single strip of gold leaf sus- 
pended within the glass bell. This is at an equal distance from the 
opposite poles of two dry piles (see Zambonv 's Dry Pile) stand- 
ing on end, one on each side of it. As soon as the leaf is excited 
it moves toward one and away from the 
other pile, and the sign of its electrification 
is shown by the direction of its motion. 

Electroscope, Condensing. A gold 
leaf electroscope, the glass bell of which 
is surmounted by an electrophorous or 
static condenser, to the lower plate of 
which the leaves of gold are suspended or 
connected. 

In use the object to be tested is touched 
to the lower plate, and the upper plate at 
the same time is touched by the finger. 
The plates are now separated. This re- 
duces the capacity of the lower plate 
greatly and its charge acquires sufficient 
potential to affect the leaves, although the 
simple touching may not have affected 
them at all. 

Electroscope, Gold Leaf. An electro- 
scope consisting of two leaves of gold leaf 
hung in contact with each other from 
the end of a conductor. When excited 
they diverge. The leaves are enclosed in 
a glass vessel. 




Fig. 160. 
Gold Leaf Electroscope. 



234 



STANDARD ELECTRICAL DICTIONARY. 



Electroscope, Pith Ball. Two pith balls suspended at opposite 
ends of a silk thread doubled in the middle. When charged with 
like electricity they repel each other. The extent of their repul- 
sion indicates the potential of their charge. 

Electrostatic Attraction and Repulsion. The attraction and 
repulsion of electrostatically charged bodies for each other, shown 
when charged with electricity. If charged with electricity of the 
same sign they repel each other. If with opposite they attract 
each other. The classic attraction and subsequent repulsion of 
bits of straw and chaff by the excited piece of amber is a case of 
electrostatic attraction and repulsion. (See Electricity ', Static — 
Electrostatics — Coulomb's Laws of Electrostatic Attraction and 
Repulsion,) 

Electrostatic Induction, Coefficient of. The coefficient 
expressing the ratio of the charge or change of charge developed in 
one body to the potential of the inducing body. 

Electrostatic Lines of Force. L,ines of force assumed to exist 



Fig. 161. Electrostatic Lines of Force Between Near Surfaces. 

in an electrostatic field of force, and to constitute the same. In 
general they correspond in action and attributes with electro- 




Fig. 162. Electrostatic Lines of Force Between Distant Surfaces. 

magnetic lines of force. They involve in almost all cases either a 
continuous circuit, or a termination at both ends in oppositely 



STANDARD ELECTRICAL DICTIONARY. 235 

charged surfaces. The cut, Fig. 161, shows the general course taken 
by lines of force between two excited surfaces when near together. 
Here most of them are straight lines reaching straight across 
from surface to surface, while a few of them arch across from near 
the edges, tending to spread. If the bodies are drawn apart the 
spreading tendency increases and the condition of things shown in 
the next cut, Fig. 162, obtains. There is an axial line whose pro- 
longations may be supposed to extend indefinitely, as occupying a 
position of unstable equilibrium. Here the existence of a straight 
and unterminated line of force may be assumed. 

A direction is predicated to lines of force corresponding with the 
direction of an electric current. They are assumed to start from a 
positively charged and to go towards a negatively charged surface. 
A positively charged body placed in an electrostatic field of force 
will be repelled from the region of positive into or towards the 
region of negative potential following the direction of the lines of 
force, not moving transversely to them, and having no transverse 
component in its motion. 

Electrostatics. The division of electric science treating of the 
phenomena of electric charge, or of electricity in repose, as con- 
trasted with electro-dynamics or electricity in motion or in current 
form. Charges of like sign repel, and of unlike sign attract each 
other. The general inductive action is explained by the use of 
the electrostatic field of force and electrostatic lines of force, q. v. 
The force of attraction and repulsion of small bodies or virtual 
points, which are near enough to each other, vary as the square of 
the distance nearly, and with the product of the quantities of the 
charges of the two bodies. 

Electrostatic Refraction. Dr. Kerr found that certain dielec- 
trics exposed to electric strain by being placed between two oppo- 
sitely excited poles of a Holtz machine or other source of very high 
tension possess double refracting powers, in other words can rotate 
a beam of polarized light, or can develop two complimentary 
beams from common light. Bisulphide of carbon shows the 
phenomenon well, acting as glass would if the glass were stretched 
in the direction of the electrostatic lines of force. To try it with 
glass, holes are drilled in a plate and wires from an influence 
machine are inserted therein. The discharge being maintained 
through the glass it polarizes light. 

Synonym — Kerr Effect. 

Electrostatic Series. A table of substances arranged in the 
order in which they are electrostatically charged by contact, 
generally by rubbing against each other. The following series is due 
to Faraday. The first members become positively excited when 



236 STANDARD ELECTRICAL DICTIONARY. 

rubbed with any of the following members, and vice versa. The 
first elements correspond to the carbon plate in a galvanic battery, 
the succeeding elements to the zinc plate. 

Cat, and Bear-skin — Flannel — Ivory — Feathers — Rock Crystal — 
Flint Glass — Cotton — Linen — Canvas — White Silk — the Hand — 
Wood — Shellac — the Metals (Iron — Copper — Brass — Tin — Silver — 
Platinum) — Sulphur. There are some irregularities. A feather 
lightly drawn over canvas is negatively electrified ; if drawn 
through folds pressed against it it is positively excited. Many 
other exceptions exist, so that the table is of little value. 

Electrostatic Stress. The stress produced upon a transparent 
medium in an electrostatic field of force by which it acquires 
double refracting or polarizing properties as regards the action of 
such medium upon light. (See Electrostatic Refraction.) 

Electrotherapeutics or Therapy. The science treating of 
the effects of electricity upon the animal system in the treat- 
ment and diagnosis of disease. 

Electrotonus. An altered condition of functional activity 
occurring in a nerve subjected to the passage of an electric current. 
If the activity is decreased, which occurs near the anode, the state 
is one of anelectrotonus ; if the activity is increased which occurs 
near the kathode the condition is one of kathelectrotonus. 

Electrotype. The reproduction of a form of type or of an 
engraving or of the like by electroplating, for printing purposes. The 
form of type is pressed upon a surface of wax contained in a shallow 
box. The wax is mixed with plumbago, and if necessary some 
more is dusted and brushed over its surface and some iron dust is 
sprinkled over it also. A matrix or impression of the type is thus 
obtained, on which copper is deposited by electroplating , q. v. 

Element, Chemical. The original forms of matter that cannot 
be separated into constituents by any known process. They are 
about seventy in number. Some of the rarer ones are being added 
to or cancelled with the progress of chemical discovery. For their 
electric relations see Electro-chemical Equivalents — Electro-chem- 
ical Series. 

The elements in entering into combination satisfy chemical 
affinity and liberate energy, which may take the form of electric 
energy as in the galvanic battery, or of heat energy, as in the 
combustion of carbon or magnesium. Therefore an uncombined 
element is the seat of potential energy. (See Energy, Potential.) 
In combining the elements always combine in definite proportions. 
A series of numbers, one being proper to each element which denote 
the smallest common multipliers of these proportions, are called 
equivalents. Taking the theory of valency into consideration the 



STANDARD ELECTRICAL DICTIONARY. 237 

product of the equivalents by the valencies gives the atomic 
weights. 

Element, Mathematical. A very small part of anything, corre- 
sponding in a general way to a differential, as the element of a 
current. 

Element of a Battery Cell. The plates in a galvanic couple are 
termed elements, as the carbon and zinc plates in a Bunsen cell. 
The plate unattacked by the solution, as the carbon plate in the 
above battery, is termed the negative plate or element ; the one 
attacked, as the zinc plate, is termed the positive plate or element. 

Synonym — Voltaic Element. 

Elements, Electrical Classification of. This may refer to 
Electro-chemical Series, Electrostatic Series, or Thermo-electric 
Series, all of which may be referred to. 

Element, Thermo=electric. One of the metals or other con- 
ductors making a thermo-electric couple, the heating of whose 
junction produces electro -motive force and a current, if on closed 
circuit. The elements of a couple are respectively positive and 
negative, and most conductors can be arranged in a series accord- 
ing to their relative polarity. (See Thermo-electric Series.) 

Elongation. The throw of the magnetic needle. (See Throw.) 
Synonym — Throw. 

Embosser, Telegraph. A telegraphic receiver giving raised 
characters on a piece of paper. It generally refers to an apparatus 



Fig. 163. Morse Receiver. 

of the old Morse receiver type, one using a dry point stylus, 
which pressing the paper into a groove in the roller above the 
paper, gave raised characters in dots and lines. 



238 



STANDARD ELECTRICAL DICTIONARY. 



E. M. D. P. Abbreviation for "electro-motive difference of 
potential " or for electro-motive force producing a current as dis- 
tinguished from mere inert potential difference. 

E. M. F. Abbreviation for " electro-motive force.", 




-> 



Fig. 164. End-on Method. 



EncUon Method. A method of determining the magnetic 
moment of a magnet. The magnet under examination, 2V S, is 
placed at right angles to the magnetic meridian, M O R, and point- 
ing directly at or " end on" to the centre of a compass needle, n s. 
From the deflection a of the latter the moment is calculated. 

Endosmose, Electric. The inflowing current of electric osmose 
(See Osmose, Electric.) 

End Play. The power to move horizontally in its bearings 
sometimes given to armature shafts. This secures a more even 
wearing of the commutator faces. End play is not permissible in 
disc armatures, as the attraction of the field upon the face of the 
armature core would displace it endwise. For such armatures 
thrust-bearings preventing end play have to be provided. 

Energy. The capacity for doing work. It is measured by work 
units which involve the exercise of force along a path of some 
length. A foot-pound, centimeter-gram, and centimeter-dyne are 
units of energy and work. 

The absolute unit of energy is the erg, a force of one dyne exer- 
cised over one centimeter of space. (See Dyne.) 

The dimensions of energy are force (M Iy/T 2 ) X space (I,) = M 
Iv 2 /T 2 . Energy may be chemical (atomic or molecular), mechan- 
ical, electrical, thermal, physical, potential, kinetic, or actual, and 
other divisions could be formulated. 

Energy, Atomic. The potential energy due to atomic 
relations set free by atomic change ; a form of chemical energy, 



STANDARD ELECTRICAL DICTIONARY. 239 

because chemistry refers to molecular as well as to atomic changes. 
When atomic energy loses the potential form it immediately 
manifests itself in some other form, such as heat or electric energy. 
It may be considered as always being potential energy. (See 
Energy, Chemical.) 

Energy, Chemical. A form of potential energy (see Energy, 
Potential) possessed by elements in virtue of their power of com- 
bining w T ith liberation of energy, as in the combination of carbon 
with oxygen in a furnace ; or by compounds in virtue of their 
power of entering into other combinations more satisfying to the 
affinities of their respective elements or to their own molecular 
affinity. Thus in a galvanic couple water is decomposed with 
absorption of energy, but its oxygen combines with zinc with evolu- 
tion of greater amount of energy, so that in a voltaic couple the 
net result is the setting free of chemical energy, which is at once 
converted into electrical energy in current form, if the battery is 
on a closed circuit. 

Energy, Conservation of. A doctrine accepted as true that 
the sum of energy in the universe is fixed and invariable. This 
precludes the possibility of perpetual motion. Energy may be 
unavailable to man, and in the universe the available energy is 
continually decreasing, but the total energy is the same and never 
changes. 

Energy, Degradation of. The reduction of energy to forms in 
which it cannot be utilized by man. It involves the reduction of 
potential energy to kinetic energy, and the reduction of kinetic 
energy of different degrees to energy of the same degree. Thus 
when the whole universe shall have attained the same temperature 
its energy will have become degraded or non-available. At present 
in the sun we have a source of kinetic energy of high degree, in 
coal a source of potential energy. The burning of all the coal 
will be an example of the reduction of potential to kinetic energy, 
and the cooling of the sun will illustrate the lowering in degree 
of kinetic energy . (See Energy, Conservation of— Energy , Poten- 
tial — En ergy , Kin etic. ) 

Energy, Electric. The capacity for doing work possessed by 
electricity under proper conditions. Electric energy may be either 
kinetic or potential. As ordinary mechanical energy is a product 
of force and space, so electric energy is a product of potential differ- 
ence and quantity. Thus a given number of coulombs of elec- 
tricity in falling a given number of volts develop electric energy. 
The dimensions are found therefore by multiplying electric current 
intensity quantity (M>^L^), by electric potential (M^L 3 / 2 /T 2 ), 
giving M I/ 2 /T 2 , the dimensions of energy in general as it should be. 

The absolute unit of electric energy in electro-magnetic measure 
is 10- 7 volt coulombs. 



240 STANDARD ELECTRICAL DICTIONARY. 

The practical unit is the volt-coulornb. As the volt is equal to io 8 
absolute units of potential and the coulomb to io- 1 absolute units 
of quantity, the volt-coulomb is equal to io 7 absolute units of 
energy. 

The volt-coulomb is very seldom used, and the unit of Electric 
Activity or Power (see Power, Electric), the volt-ampere, is uni- 
versally used. This unit is sometimes called the Watt, q. v., and 
it indicates the rate of expenditure or of production of electric 
energy. 

The storing up in a static accumulator or condenser of a given 
charge of electricity, available for use with a given change of poten- 
tial represents potential electric energy. 

The passing of a given quantity through a conductor with a 
given fall of potential represents kinetic electric energy. 

In a secondary battery there is no storage of energy, but the 
charging current simply accumulates potential chemical energy in 
the battery, which chemical energy is converted into electric energy 
in the discharge or delivery of the battery. 

It is customary to discuss Ohm's law in this connection ; it is 
properly treated under Electric Power, to which the reader is 
referred. (See Power, Electric.) 

Energy, Electric Transmission of. If an electric current 
passes through a conductor all its energy is expended in the full 
circuit. Part of the circuit may be an electrical generator that 
supplies energy as fast as expended. Part of the circuit may be a 
motor which absorbs part of the energy, the rest being expended in 
forcing a current through the connecting wires and through the 
generator. The electric energy in the generator and connecting 
wires is uselessly expended by conversion into heat. That in the 
motor in great part is utilized by conversion into mechanical 
energy which can do useful work. This represents *the transmis- 
sion of energy. Every electric current system represents this 
operation, but the term is usually restricted to the transmission of 
comparatively large quantities of energy. 

A typical installation might be represented thus. At a waterfall 
a turbine water wheel is established which drives a dynamo. From 
the dynamo wires are carried to a distant factory, where a motor or 
several motors are established, which receive current from the dyna- 
mo and drive the machinery. The same current, if there is enough 
energy, may be used for running lamps or electroplating. As elec- 
tric energy (see Energy, Electric,) is measured by the product of 
potential difference by quantity, a very small wire will suffice for 
the transmission of a small current at a high potential, giving a 
comparatively large quantity of energy. It is calculated that the 
energy of Niagara Falls could be transmitted through a circuit of 



STANDARD ELECTRICAL DICTIONARY. 241 

iron telegraph wire a distance of over 1,000 miles, but a potential 
difference of 135,000,000 volts would be required, something quite 
impossible to obtain or manage. 

Energy, Kinetic. Energy due to matter being actually in 

motion. It is sometimes called actual energy. The energy varies 

directly with the mass and with the square of the velocity. It is 

represented in formula by y z m z/ 2 . 

Synonyms — Actual Energy — Energy of Motion — Dynamic Energy. 

Energy, Mechanical. The energy due to mechanical change 
or motion, virtually the same as molar energy. (See Energy, 
Molar.) 

Energy, Molar. The energy of masses of matter due to move- 
ments of or positions of matter in" masses ; such as the kinetic energy 
of a pound or of a ton in motion, or the potential energy of a 
pound at an elevation of one hundred feet. 

Energy, Molecular. The potential energy due to the relations 
of molecules and set free by their change in the way of combina- 
tion. It is potential for the same reason that applies to atomic 
and chemical energy, of which latter it is often a form, although it is 
often physical energy. The potential energy stored up in vaporization 
is physical and molecular energy ; the potential energy stored up in 
uncombined potassium oxide and water, or calcium oxide (quick- 
lime) and water is molecular, and when either two substances are 
brought together kinetic, thermal or heat energy is set free, as in 
slaking lime for mortar. 

Energy of an Electrified Body. An electrified body implies 
the other two elements of a condenser. It is the seat of energy set 
free when discharged. (See Dielectric, Energy of.) The two oppo- 
sitely charged bodies tend to approach. This tendency, together 
with the distances separating them, represents a potential energy. 

Energy of Stress. Potential energy due to stress, as the stretch- 
ing of a spring. This is hardly a form of potential energy. A 
stressed spring is merely in a position to do work at the expense 
of its own thermal or kinetic energy because it is cooled in doing 
work. If it possessed true potential energy of stress it would not 
be so cooled. 

Energy of Position. Potential energy due to position, as the 
potential energy of a pound weight raised ten feet (ten foot lbs.). 
(See Energy, Potential.) 

Energy, Physical. The potential energy stored up in physical 
position or set free in physical change. Thus a vapor or gas absorbs 
energy in its vaporization, which is potential energy, and appears 
as heat energy when the vapor liquefies. 

Energy, Potential, or Static Energy. The capacity for doing 
work in a system due to advantage of position or other cause, such 



242 STANDARD ELECTRICAL DICTIONARY. 

as the stress of a spring. A pound weight supported ten feet 
above a plane has ten foot lbs. of potential energy of position 
referred to that plane. A given weight of an elementary substance 
represents potential chemical energy, which will be liberated as 
actual energy in its combination with some other element for 
which it has an affinity. Thus a ton of coal represents a quantity 
of potential chemical energy which appears in the kinetic form of 
thermal energy when the coal is burning in a furnace. A charged 
L,eyden jar represents a source of potential electric energy, which 
becomes kinetic heat energy as the same is discharged. 

Energy, Thermal. A form of kinetic molecular energy due to 
the molecular motion of bodies caused by heat. 

Entropy. Non-available energy. As energy may in some 
way or other be generally reduced to heat, it will be found that 
the equalizing of temperature, actual and potential, in a system, 
while it leaves the total energy unchanged, makes it all unavailable, 
because all work represents a fall in degree of energy or a fall in 
temperature. But in a system such as described no such fall could 
occur, therefore no work could be done. The universe is obviously 
tending in that direction. On the earth the exhaustion of coal 
is in the direction of degradation of its high potential energy, so 
that the entropy of the universe tends to zero. (See Energy, Degra- 
dation of) 




Fig. 165. Epinus' Condenser. 

Entropy, Electric. Clerk Maxwell thought it possible to recog- 
nize in the Peltier effect, q. v., a change in entropy, a gain or loss 
according to whether the thermo-electric junction was heated 
or cooled. This is termed Electric Entropy. (See Energy, 
Degradation of.) 

Epinus' Condenser. Two circular brass plates, A and B, are 
mounted on insulating supports, and arranged to be moved towards 
or away from each other as desired. Between them is a plate of 



STANDARD ELECTRICAL DICTIONARY. 



243 



glass, C, or other dielectric. Pith balls may be suspended back of 
each brass plate as shown. The apparatus is charged by connecting 
one plate to an electric machine and the other to the earth. The 




Fig. 166. Epinus' Condenser. 

capacity of the plate connected to the machine is increased by 
bringing near to it the grounded plate, by virtue of the principle of 
bound charges. This apparatus is used to illustrate the prin- 
ciples of the electric condenser. It was invented after the Ley den 
jar was invented. 

E. P. S. Initials of Electrical Power Storage ; applied to a type 
of secondary battery made by a company bearing that title. 




Fig. 167. Cam Equalizer. 

Equalizer. In electro-magnetic mechanism an arrangement 



244 STANDARD ELECTRICAL DICTIONARY. 

for converting the pull of the electro-magnet varying in intensity 
greatly over its range of action, into a pull of sensibly equal strength 
throughout. The use of a rocking lever acting as a cam, with 
leverage varying as the armature approaches or recedes from the 
magnet core is one method of effecting the result. Such is shown 
in the cut. E is an electro-magnet, with armature a. A and B 
are the equalizer cams. The pull on the short end of the cam B is 
sensibly equal for its whole length. 

Many other methods have been devised, involving different 
shapes of pole pieces, armatures or mechanical devices other than 
the one just shown. 

Equipotential. adj. Equal in potential ; generally applied to 
surfaces. Thus every magnetic field is assumed to be made up of 
- lines of force and intersecting those lines, surfaces, plane, or more 
or less curved in contour, can be determined, over all parts of 
each one of which the magnetic intensity will be identical. 
Each surface is the locus of equal intensity. The same type of 
surface can be constructed for any field of force, such as an electro- 
static field, and is termed an equipotential surface. 

Equipotential Surface, Electrostatic. A surface in an electro- 
static field of force, which is the locus of all points of a given poten- 
tial in such field ; a surface cutting all the lines of force at a point 
of identical potential. Lines of force are cut perpendicularly by 
an equipotential surface, or are normal thereto. 

Equipotential Surface, Magnetic and Electro=magnetic. A 

surface bearing the same relation to a magnetic or electro-magnetic 
field of force that an electrostatic equipotential surface (see Equi- 
potential Surface, Electrostatic,) does to an electrostatic field of 
force. 

Equivalent, Chemical. The quotient obtained by dividing the 
atomic weight of an element by its valency. 

Equivalents, Electrochemical. The weight of any substance 
set free by one coulomb of electricity. The following give some 
equivalents expressed in milligrams : 

Hydrogen .0105 Mercury (mercurous) 2.10 

Gold .6877 Iron (ferric) .1964 

Silver 1*134 Iron (ferrous) .294 

Copper (cupric) -3307 Nickel -3098 

Mercury (mercuric) 1.05 Zinc .34 13 

I,ead 1.0868 Chlorine -37 2 8 

Oxygen .o84 

Equivalent, Electro=mechanical. The work or energy equiv- 
alent to unit quantities of electric energy, q. v. ; or equivalent to a 
unit current in a conductor whose ends differ one unit of potential. 



STANDARD ELECTRICAL DICTIONARY. 245 

The unit of electric energy taken is the watt-second or volt-cou- 
lomb. One volt-coulomb is equal to 

Ergs io 7 Foot Pound -737337 

Gram-degree C. .24068 Horse Power Second .0013406 

Pound-degree F. .000955 

One horse power is equal to 745.943 volt coulombs per second. 

Equivalent, Electrothermal. The heat produced by a unit 
current passing through a conductor with unit difference of poten- 
tial at its ends ; the heat equivalent of a volt-coulomb or watt- 
second. It is equal to Gram-degree C. .24068 
Pound-degree F. .000955 

Equivalent, Thermo=chemical. The calories evolved by the 
combination of one gram of any substance with its equivalent of 
another substance being determined, the product obtained by mul- 
tiplying this number by the equivalent (atomic or molecular 
weight ~ valency) of the first element or substance is the thermo- 
chemical equivalent. If expressed in kilogram calories, the 
product of the thermo-chemical equivalent by 0.43 gives the volt- 
age required to effect such decomposition. 

The following are thermo-chemical equivalents of a few com- 
binations : 

Water 34.5 Zinc oxide 43.2 

Iron protoxide 34.5 Iron Sesquioxide 31.9X3 

Copper oxide 19.2 

Equivolt. " The mechanical energy of one volt electro-motive 
force exerted under unit conditions through one equivalent of 
chemical action in grains." (J. T. Sprague.) This unit is not in 
general use as the unit of electric energy, the volt-coulomb and 
(for rate of electric energy) the volt-ampere being always used. 

Erg. The absolute or fundamental C. G. S. unit of work or 
energy. The work done or energy expended in moving a body 
through one centimeter against a resistance of one dyne. 

Erg=ten. Ten millions of ergs, or ten meg-ergs. 

Escape. A term applied to leakage of current. ■ 

Etching, Electric. A process of producing an etched plate. 
The plate is coated with wax, and the design traced through as in 
common etching. It is then placed in a bath and is connected to 
the positive terminal from a generator, whose negative is im- 
mersed in the same bath, so that the metal is dissolved by electrolytic 
action. By attaching to the other terminal and using a plating 
bath, a rough relief plate may be secured, by deposition in the 
lines of metal by electroplating. 

Synonym — Electric Engraving. 



246 STANDARD ELECTRICAL DICTIONARY. 

Ether. The ether is a hypothetical thing that was invented to 
explain the phenomena of light. Light is theoretically due to 
transverse vibrations of the ether. Since the days of Young the 
conception of the ether has extended, and now light, i 'radiant heat, ' ' 
and electricity are all treated as phenomena of the ether. Elec- 
trical attraction and repulsion are explained by considering them 
due to local stresses in the ether ; magnetic phenomena as due to 
local whirlpools therein. The ether was originally called the 
luminiferous ether, but the adjective should now be dropped. Its 
density is put at 936X10 — 21 that of water, or equal to that of 
the atmosphere at 210 miles above the earth's surface. Its rigidity 
is about 10 — 9 that of steel (see Ten, Powers of) ; as a whole it is 
comparable to an all-pervading jelly, with almost perfect elas- 
ticity. The most complete vacuum is filled with ether. 

All this is a hypothesis, for the ether has never been proved to 
exist. Whether gravitation will ever be explained by it remains 
to be seen. 

Eudiometer. A graduated glass tube for measuring the volumes 
of gases. In its simplest form it is simply a cylindrical tube, with a 
scale etched or engraved upon it, closed at one end and open at the 
other. The gas to be measured is collected in it over a liquid, 
generally water, dilute sulphuric acid in the gas voltameter, or 
mercury. Many different shapes have been given them by Hoff- 
mann, Ure, Bunsen and others. 

Evaporation, Electric. The superficial sublimation or evapora- 
tion of a substance under the influence of negative electricity. It 
is one of the effects investigated by Crookes in his experiments 
with high vacua. He found that when a metal, even so infu- 
sible as platinum, was exposed to negative electrification in one of 
his high vacuum tubes, that it was volatilized perceptibly. A cad- 
mium electrode heated and electrified, negatively was found to 
give a strong coating of metal on the walls of the tube. Even in 
the open air the evaporation of water was found to be accelerated 
by negative electrification. 

Exchange, Telephone. The office to which telephone wires 
lead in a general telephone system. In the office by a multiple 
switch board, or other means, the different telephones are inter- 
connected by the office attendants, so that any customers who 
desire it may be put into communication with each other. The 
exchange is often termed the Central Office, although it may be 
only a branch office. 

Excitability, Faradic. The action produced in nerve or 
muscle of the animal system by an alternating or intermitting high 
potential discharge from an induction coil. 



STANDARD ELECTRICAL DICTIONARY. 247 

Excitability, Galvanic. The same as Faradic excitability, except 
that it refers to the effects of the current from a galvanic battery. 

Excitability of Animal System, Electric. The susceptibility 
of a nerve or muscle to electric current shown by the effect pro- 
duced by its application. 

Exciter. A generator used for exciting the field magnet of a 
dynamo. In alternating current dynamos, e. g., of the Westing- 
house type, a special dynamo is used simply to excite the field 
magnet. In central station distribution the same is often done for 
direct current dynamos. 

Exosmose, Electric. The outflowing current of electric osmose. 
(See Osmose , Electric) 

Expansion, Coefficient of. The number expressing the propor- 
tional increase in size, either length, area or volume, of a substance 
under the influence generally of heat. There are three sets 
of coefficients, (1) of linear expansion, (2) of superficial expansion, 
(3) of cubic expansion or expansion of volume. The first and 
third are the only ones much used. They vary for different sub- 
stances, and for the same substance at different temperatures. They 
are usually expressed as decimals indicating the mixed number 
referred to the length or volume of the body at the freezing point 
as unity. 

Expansion, Electric, (a) The increase in volume of a con- 
denser, when charged electrostatically. A Leyden jar expands 
when charged, and contracts when discharged. 

(6) The increase in length of a bar of iron when magnetized. 
This is more properly called magnetic expansion or magnetic 
elongation. 

Exploder, (a) A small magneto-generator for producing a 
current for heating the wire in an electric fuse of the Abel type 
(see Fuse, Electric), and thereby determining an explosion. 

(b) The term may also be applied to a small frictional or influ- 
ence machine for producing a spark for exploding a spark fuse. 

Explorer. A coil, similar to a magnetizing coil (see Coil, 
Magnetizing), used for investigating the electro- magnetic circuit 
and for similar purposes. If placed around an electro-magnet and 
connected with a galvanometer, it will produce a deflection, owing 
to a momentary induced current, upon any change in the magnet, 
such as removing or replacing the armature. It is useful in deter- 
mining the leakage of lines of force and for general investigations 
of that nature. It is often called an exploring coil. Hughes' In- 
duction Balance (see Induction Balance, Hughes') is sometimes 
called a Magnetic Explorer. The exploring coil may be put in 



248 STANDARD ELECTRICAL DICTIONARY. 

circuit with a galvanometer for quantitative measurements or with 
a telephone for qualitative ones. 

Extension Bell Call. A system of relay connection, q. v., by 
which a bell is made to continue ringing after the current has 
ceased coming over the main line. It is designed to prolong 
the alarm given by a magneto call bell, q. v., which latter only 
rings as long as the magneto handle is turned. A vibrating elec- 
tric bell (see Bell, Electric,) is connected in circuit with a local 
battery and a switch normally open, but so constructed as to close 
the circuit when a current is passed and continue to do so indefin- 
itely. The distant circuit is connected to this switch. When 
the magneto is worked it acts upon the switch, closes the local bat- 
tery circuit and leaves it closed, while the bell goes on ringing 
until the battery is exhausted or the switch is opened by hand. 

Eye, Electro=magnetic. An apparatus used in exploring a field 
of electro-magnetic radiations. It is a piece of copper wire 2 milli- 
meters (.08 inch) in diameter, bent into an almost complete circle 
70 millimeters (.28 inch) in diameter, with terminals separated by 
an air gap. This is moved about in the region under examination, 
and by the production of a spark indicates the locality of the loops 
or venters in systems of stationary waves. 

F. Abbreviation for Fahrenheit, as io° F., meaning io° Fahren- 
heit. (See Fahrenheit Scale.) 

Fahrenheit Scale. A thermometer scale in use in the United 
States and England. On this scale the temperature of melting ice 
is32° ; that of condensing steam is2i2° ; the degrees are all of equal 
length. Its use is indicated by the lettei F., as 180 F. To con- 
vert its readings into centigrade, subtract 32 and multiply by 5/9. 
(b) To convert centigrade into F. multiply by 9/5 and add 32. Thus 
180 F. = (180-32) X 5/9 C. = 82ft C. Again 188 C. = (180 + 9/5) 
-f- 32 — 324 F. The additions and subtractions must be algebraie 
in all cases. Thus when the degrees are minus or below zero the 
rules for conversion might be put thus : To convert degrees F. 
below zero into centigrade to the number of degrees F. add 32, 
multiply by 5/9 and place a minus sign ( — ) before it. (b) To con- 
vert degrees centigrade below zero into Fahrenheit, multiply the 
number of degrees by 9/5, subtract from 32 if smaller; if greater than 
32 subtract 32 therefrom, and prefix a minus sign, thus : — io° C. 
= 32 — (10 X 9/5) = 14°. Again, — 3o°C. = (30 X 9/5) — 32 = 

22 =— 22° F. 

Farad. The practical unit of electric capacity ; the capacity 
of a conductor which can retain one coulomb of electricity at a 
potential of one volt. 

The quantity of electricity charged upon a conducting surface 



STANDARD ELECTRICAL DICTIONARY. 249 

raises its potential ; therefore a conductor of one farad capacity 
can hold two coulombs at two volts potential, and three coulombs 
at three volts, and so on. The electric capacity of a conductor, 
therefore, is relative compared to others as regards its charge, for 
the latter may be as great as compatible w r ith absence of sparking 
and disruptive discharge. In other words, a one farad or two farad 
conductor may hold a great many coulombs. Charging a conductor 
with electricity is comparable to pumping air into a receiver. 
Such a vessel may hold one cubic foot of air at atmospheric pressure 
and two at two atmospheres, and yet be of one cubic foot capacity 
however much air is pumped into it. 

The farad is equal to one fundamental electrostatic unit of capacity 
multiplied by 9 X io 11 and to one electro-magnetic unitmutiplied 
by io- 9 . 

The farad although one of the practical units is far too large, so the 
micro-farad is used in its place. The capacity of a sphere the size 
of the earth is only tfotHtoo" °f a farad. 

Faraday, Effect. The effect of rotation of its plane produced 
upon a polarized beam of light by passage through a magnetic 
field. (See Magnetic Rotary Polarization . ) 

Faraday's Cube. To determine the surface action of a charge, 
Faraday constructed a room, twelve feet cube, insulated, and lined 
with tinfoil. This room he charged to a high potential, but within 
it he could detect no excitement whatever. The reason was because 
the. electricity induced in the bodies within the room was exactly 
equal to the charge of the room-surface, and was bound exactly by it. 
The room is termed Faraday's cube. 

Faraday's Dark Space. A non-luminous space between the 
negative and positive glows, produced in an incompletely exhausted 
tube through which a static discharge, as from an induction coil, is 
produced. It is perceptible in a rarefaction of 6 millimeters (.24 inch) 
and upwards. If the exhaustion is very high a dark space appears 
between the negative electrode and its discharge. This is known 
as Crook es' dark space. 

Faraday's Disc. A disc of any metal, mounted so as to be sus- 
ceptible of rotation in a magnetic field of force, with its axis 
parallel to the general direction of the lines of force. A spring 
bears against its periphery and another spring against its axle. 
When rotated, if the springs are connected by a conductor, a current 
is established through the circuit including the disc and conductor. 
The radius of the disc between the spring contacts represents a 
conductor cutting lines of force and generating a potential differ- 
ence, producing a current. If a current is sent through the motion- 
less wheel from centre to periphery it rotates, illustrating the 



250 



STANDARD ELECTRICAL DICTIONARY. 



doctrine of reversibility. As a motor it is called Barlow's or Stur- 
geon's Wheel. If the disc without connections is rapidly rotated 

it produces Foucault currents, q. v., 
within its mass, which resist its rotation 
and heat the disc. 

Faraday's Net. An apparatus for 
showing that the electric charge resides 
on the surface. It consists of a net, 
conical in shape and rather deep, to 
whose apex two threads, one on each 
side, are attached. Its mouth is fast- 
ened to a vertical ring and the whole is 
mounted on an insulating support. 

It is pulled out to its full extent and 
is electrified. No charge can be detected 
inside it. By pulling one of the threads 
it is turned with the other side out. 
Now all the charge is found on the out- 
side just as before, except that it is of 
course on the former inside surface of 
the bag. The interior shows no charge. 




Fig. i 



Faraday's Net." 



Faraday's Transformer. The first transformer. It was made 
by Michael Faraday. It was a ring of soft iron 7/% inch thick, 
and 6 inches in external diameter. It was wound with bare wire, 
calico being used to prevent contact of the wire with the ring and 
of the layers- of wire with each other, while twine was wound 
between the convolutions to prevent the wires from touching. 
Seventy-two feet of copper wire, ^ inch diameter, were wound in 
three superimposed coils, covering about one-half of the ring. On 
the other half sixty feet of copper wire were wound in two super- 
imposed coils. Faraday connected his coils in different ways and 
used a galvanometer to measure the current produced by making 
and breaking one of the circuits used as a primary. 

The coil is of historic interest. 

Faraday's Voltameter. A voltameter, in which the coulombs of 
current are measured by the volume of the gas evolved from acidu- 
lated water. "(See Voltameter ', Gas.) 

Faradic. adj. Referring to induced currents, produced from 
induction coils. As Faraday was the original investigator of the 
phenomena of electro-magnetic induction, the secondary or 
induced electro-magnetic currents and their phenomena and 
apparatus are often qualified by the adjective Faradic, especially in 
electro-therapeutics. A series of alternating electrostatic dis- 
charges, as from an influence machine (Holtz), are sometimes called 



STANDARD ELECTRICAL DICTIONARY. 251 

Franklinic currents. They are virtually Faradic, except as 
regards their production. 

Faradic Brush. A brush for application of electricity to the 
person. It is connected as one of the electrodes of an induction 
coil or magneto generator. For bristles wire of nickel plated 
copper is generally employed. 

Faradization. In medical electricity the analogue of galvan- 
ization; the effects due to secondary or induced currents ; galvan- 
ization referring to currents from a galvanic battery; also the process 
of application of such currents. 

Faults. Sources of loss of current or of increased resistance or 
other troubles in electric circuits. 

Feeder. A lead in an electric central station distribution 
system, which lead runs from the station to some point in the dis- 
trict to supply current. It is not used for any side connections, 
but runs direct to the point where current is required, thus " feed- 
ing ' ' the district directly. In the two wire system a feeder may 
be positive or negative ; in the three wire system there is also a 
neutral feeder. Often the term feeder includes the group of two 
or of three parallel lines. 

Feeder Equalizer. An adjustable resistance connected in cir- 
cuit with a feeder at the central station. The object of the feeder 
being to maintain a definite potential difference at its termination, 
the resistance has to be varied according to the current it is called 
on to carry. 

Feeder, Main or Standard. The main feeder of a district. 
The standard regulation of pressure (potential difference between 
leads) in the district is often determined by the pressure at the end 
of the feeder. 

Feeder, Negative. The lead or wire in a set of feeders, which 
is connected to the negative terminal of the generator. 

Feeder, Neutral. In the three wire system the neutral wire in a 
set of feeders. It is often made of less diameter than the positive 
and negative leads. 

Feeder, Positive. The lead or wire in a set of feeders, which 
wire is connected to the positive terminal of the generator. 

Ferranti Effect. An effect as yet not definitely explained, 
observed in the mains of the Deptford, Eng. , alternating current 
plant. It is observed that the potential difference between the 
members of a pair of mains rises or increases with the distance the 
place of trial is from the station. 



252 STANDARD ELECTRICAL DICTIONARY. 

Ferro= magnetic, adj. Paramagnetic ; possessing the magnetic 
polarity of iron. 

Fibre and Spring Suspension. A suspension of the galvanom- 
eter needle used in marine galvanometers. The needle is sup- 
ported at its centre of gravity by a vertically stretched fibre 
attached at both its ends, but with a spring intercalated between the 
needle and one section of the fibre. 

Fibre Suspension. Suspension, as of a galvanometer needle, 
by a vertical or hanging fibre of silk or cocoon .fibre, or a quartz 
fibre. (See Quartz.) 

This suspension, while the most delicate and reliable known, is 
very subject to disturbance and exacts accurate levelling of the 
instrument. 

Fibre suspension is always characterized by a restitutive force. 
Pivot suspension, q. v., on the other hand, has no such force. 

Field, Air. A field the lines of force of which pass through 
air ; the position of a field comprised within a volume of air. 

Field, Alternating. Polarity or direction being attributed to 
lines of force, if such polarity is rapidly reversed, an alternating 
field results. Such field may be of any kind, electro-magnetic or 
electrostatic. In one instance the latter is of interest. It is sup- 
posed to be produced by high frequency discharges of the secondary 
of an induction coil, existing in the vicinity of the discharging 
terminals. 

Field Density. Field density or density of field is expressed in 
lines of force per unit area of cross-section perpendicular to the 
lines of force. 

Field, Distortion of. The lines of force reaching from pole to 
pole of an excited field magnet of a dynamo are normally symmet- 
rical with respect to some axis and often with respect to several. 
They go across from pole to pole, sometimes bent out of their 
course by the armature core, but still symmetrical. The presence 
of a mass of iron in the space between the pole pieces concentrates 
the lines of force, but does not destroy the symmetry of the field. 

When the armature of the dynamo is rotated the field becomes 
distorted, and the lines of force are bent out of their natural shape. 
The new directions of the lines of force are a resultant of the lines 
of force of the armature proper and of the field magnet. For 
when the dynamo is started the armature itself becomes a magnet, 
and plays its part in forming the field. Owing to the lead of the 
brushes the polarity of the armature is not symmetrical with that 
of the field magnets. Hence the compound field shows distortion. 



STANDARD ELECTRICAL DICTIONARY. 



253 



In the cut is shown diagrammatically the distortion of field in a 
dynamo with a ring armature. The arrow denotes the direction of 
rotation, and n n * * * and ii* ** indicate points of north and 




Fig.: 



Distortion of Field in a Ring Armature of an Active Dynamo. 



south polarity respectively. The distorted lines must be regarded as 
resultants of the two induced polarities of the armature, one polarity 




-***' 



Fig. 170. Distortion of Field in a Ring "Armature of an Active Motor. 

due to the induction of the field, the other to the induction from 
its own windings. The positions of the brushes have much to do 



254 STANDARD ELECTRICAL DICTIONARY. 

with determining the amount and degree of distortion. In the 
case of the ring armature it will be seen that some of the lines of 
force within the armature persist in their polarity and direction, 
almost as induced by the armature windings alone, and leak 
across without contributing their quota to the field. Two such 
lines are shown in dotted lines. 

In motors there is a similar but a reversed distortion. 

Field, Drag of. When a conductor is moved through a field so 
that a current is generated in it, the field due to that current blends 
with the other field and with its lines of force, distorting the field, 
thereby producing a drag upon its own motion, because lines of 
force always tend to straighten themselves, and the straightening 
would represent cessation of motion in the conductor. This ten- 
dency to straightening therefore resists the motion of the conduc- 
tor and acts a drag upon it. 

Field of Force. The space in the neighborhood of an attracting 
or repelling mass or system. Of electric fields of force there are two 
kinds, the Electrostatic and the Magnetic Fields of Force, both of 
which may be referred to. A field of force may be laid out as a 
collection of elements termed Lines of Force, and this nomenclature 
is universally adopted in electricity. The system of lines may be 
so constructed that (a) the work done in passing from one equipo- 
tential surface to the next is always the same ; or (b) the lines of 
force are so laid out and distributed that at a place in which unit 
force is exercised there is a single line of force passing through the 
corresponding equipotential surface in each unit of area of that sur- 
face. The latter is the universal method in describing electric 
fields. It secures the following advantages : — First : The potential 
at any point in the field of space surrounding the attracting or 
repelling mass or masses is found by determining on which 
imaginary equipotential surface that point lies. Second : If unit- 
length of a line of force cross n equipotential surfaces, the mean 
force along that line along the course of that part of it is equal to n 
units ; for the difference of potential of the two ends of that part of 
the line of force = n ; it is also equal to F s (F = force), because 
it represents numerically a certain amount of work; but s=i, 
whence n = F. Third : The force at any part of the field corre- 
sponds to the extent to which the lines of force are crowded 
together ; and thence it may be determined by the number of lines 
of force which pass through a unit of area of the corresponding 
equipotential surface, that area being so chosen as to comprise the 
point in question. (Daniell.) 

Field of Force, Electrostatic. The field established by the 
attracting, repelling and stressing influence of an electrostatically 
charged body. It is often termed an Electrostatic Field. (See 
Field of Force.) 



STANDARD ELECTRICAL DICTIONARY. 



255 



Field of Force of a Current. A current establishes a field of 
force around itself, whose lines of force form circles with their 
centres on the axis of the current. The cut, Fig. 172, shows the 
relation of lines of force to current. 



^JIJIJUL^M^ 




^i^^SWt- 



Fig. I7I# Experiment Showing Lines 
of Force Surrounding an Active 
Conductor. 



Fig. 172. Diagram of Field 
of Force Surrounding an 
Active Conductor. 



The existence of the field is easily shown by passing a conductor 
vertically through a horizontal card. On causing a current to go 
through the wire the field is formed, and iron filings dropped upon 
the card, tend, when the latter is gently tapped, to take the form of 
circles. The experiment gives a version of the well-known mag- 
netic figures, q. v. See Fig. 171. 




Fig. 173. Line of Force Induced by a Current Showing the Magnetic 
Whirls. 

The cut shows by the arrows the relation of directions of current 
to the direction of' the lines of force, both being assumptions, and 



256 STANDARD ELECTRICAL DICTIONARY. 

merely indicating certain fixed relations, corresponding exactly to 
the relations expressed by the directions of electro-magnetic or 
magnetic lines of force. 

Field, Pulsatory. A field produced by pulsatory currents. By 
induction such field can produce an alternating current. 

Field, Rotating. In a dynamo the field magnets are sometimes 
rotated instead of the armature, the latter being stationary. In 
Mordey's alternator the armature, nearly cylindrical, surrounds the 
field, and the latter rotates within it, the arrangement being nearly 
the exact reverse of the ordinary one. This produces a rotating field. 

Field, Rotatory. A magnetic field whose virtual poles keep 
rotating around its centre of figure. If two alternating currents 
differing one quarter period in phase are carried around four mag- 
netizing coils placed and connected in sets of two on the same 
diameter and at right angles to each other, the polarity of the sys- 
tem will be a resultant of the combination of their polarity, and 
the resultant poles will travel round and round in a circle. In such 
a field, owing to eddy currents, masses of metal, journal ed like an 
armature, will rotate, with the speed of rotation of the field. 

Field, Stray. The portion of afield of force outside of the reg- 
ular circuit ; especially applied to the magnetic field of force of 
dynamos expressing the portion which contributes nothing to the 
current generation. 

Synonym — Waste Field. 

Field, Uniform. A field of force of uniform density. (See 
Field Density.) 

Figure of Merit. In the case of a galvanometer, a coefficient 
expressing its delicacy. It is the reciprocal of the current required 
to deflect the needle through one degree. By using the reciprocal 
the smaller the current required the larger is the figure of merit. 
The same term may be applied to other instruments. 

It is often defined as the resistance of a circuit through which 
one Daniell's element will produce a deflection of one degree on 
the scale of the instrument. The circuit includes a Daniell's cell 
of resistance r, a rheostat R, galvanometer G and shunt S. Assume 
that with the shunt in parallel a deflection of d divisions is 
obtained. The resistance of the shunted galvanometer is G S/G-[-S ; 
the multiplying power m of the shunt is S+G/S ; the formula or 
figure of merit is m d (r+R +G S/G+S). . 

The figure of merit is larger as the instrument is more sensitive. 

Synonym — Formula of Merit. 

Filament. A thin long piece of a solid substance. In general it is 



STANDARD ELECTRICAL DICTIONARY. 257 

so thin as to act almost like a thread, to be capable of standing con- 
siderable flexure. The distinction between filament and rod has 
been of much importance in some patent cases concerning incan- 
descent lamps. As used by electricians the term generally applies 
to the carbon filament of incandescent lamps. This as now made 
has not necessarily any fibres, but is entitled to the name of fila- 
ment, partly by convention, partly by its relative thinness and want 
of stiffness. (See Incandescent Lamps — Magnetic Filament.) 

Fire Alarm, Electric, Automatic. A system of telegraph cir- 
cuits, at intervals supplied with thermostats or other apparatus 
affected by a change of temperature, which on being heated closes 
the circuit and causes a bell to ring. (See Thermostat.) 

Fire Alarm Telegraph System. A system of telegraphic lines 
for communicating the approximate location of a fire to a central 
station and thence to the separate fire-engine houses in a city or 
district. It includes alarm boxes, distributed at frequent intervals, 
locked, with the place wmere the key is kept designated, or in some 
systems left unlocked. On opening the door of the box and pull- 
ing the handle or otherwise operating the alarm, a designated 
signal is sent to the central station. From this it is telegraphed 
by apparatus worked by the central station operator to the engine 
houses. The engines respond according to the discipline of the 
service. 

Fire Cleansing. Freeing the surface of an article to be plated 
from grease by heating. 

Fire Extinguisher, Electric, Automatic. A modification of 
the electric fire alarm (see Fire Alarm, Electric , Automatic) , in 
which the thermostats completing the circuits turn on water 
which, escaping through the building, is supposed to reach and 
extinguish a fire. 

Flashing in a Dynamo or Magneto=electric Generator. Bad 

adjustment of the brushes at the commutator, or other fault of 
construction causes the production of voltaic arcs at the com- 
mutator of a generator, to which the term flashing is applied. 

Flashing of Incandescent Lamp Carbons. A process of treat- 
ment for the filaments of incandescent lamps. The chamber 
before sealing up is filled with a hydro-carbon vapor or gas, such 
as the vapor of a very light naphtha (rhigolene). A current is then 
passed through the filament heating it to redness. The more 
attenuated parts or those of highest resistance are heated the 
highest, and decompose most rapidly the hydro-carbon vapor, 
graphitic carbon being deposited upon these parts, while hydrogen 
is set free. This goes on until the filament is of uniform resistance 
throughout. It gives also a way of making the resistance of the 



258 STANDARD EIvKCTRICAIy DICTIONARY. 

filament equal to any desired number of ohms, provided it is 
originally of high enough resistance. The process increases the 
conductivity of the filament. 

After flashing the chambers are pumped out and sealed up. 

Flashing Over. A phenomenon observed in high potential 
dynamos. On a sudden alteration of the resistance of the circuit a 
long blue spark will be drawn out around the surface of the com- 
mutator from brush to brush. The spark is somewhat of the nature 
of an arc, and may seriously injure commutators whose sections 
are only separated by mica, or other thin insulation. In the case 
of commutators whose sections are separated by air spaces it is not 
so injurious. 

Flats. In a commutator of a dynamo, the burning or wearing 
away of a commutator segment to a lower level than the rest. 
Sometimes two adjacent bars will be thus affected, causing a flat 
place on the commutator. It is not always easy to account for the 
formation of flats. They may have their origin in periodic vibra- 
tions due to bad mounting, or to sparking at the particular point. 

Floor Push. A press or push button constructed to be set into 
the floor to be operated by pressing with the foot. It is used to 
ring an alarm bell, sound a buzzer or for similar service. 

Fluid, Depolarizing. A fluid used in voltaic batteries to dis- 
pose of the hydrogen, which goes to the negative plate. This it 
does by oxidizing it. Chromic acid, nitric acid, and chloric acids 
are among the constituents of liquid depolarizers. (See Electro- 
poion Fluid.) 

Fluid, Electric. The electric current and charge have some- 
times been attributed to a fluid. The theory, which never was much 
more than hypothetical, survives to some extent in the single and 
double fluid theory. (See Single Fluid Theory — Double Fluid 
Theory.) 

Fluorescence. The property of converting ether waves of one 
length, sometimes of invisible length, into waves of another 
length (visible). ^Esculin, quinine salts, uranium glass and other 
substances exhibit this phenomenon. The phenomenon is utilized 
in the production of Geissler tubes. 

Flush Boxes. A heavy iron box covered with a heavy hand 
plate and laid flush (whence the name), or even with the surface 
of a roadway. Into it conductors of an underground system lead, 
and it is used to make connections therewith and for examining 
the leakage of the conductors and for similar purposes. It is a 
" man-hole " (q. v.) in miniature. 



STANDARD ELECTRICAL DICTIONARY. 259 

Fluviograph. An electric registering tide gauge or water level 
gauge. 

Fly or Flyer, Electric. A little wheel, ordinarily poised on £ 
point, like a compass needle. It carries several tangentially 
directed points, all pointing in the same sense. When connected 
with a source of electricity of high potential it revolves by reac- 
tion. The tension of its charge is highest at the points, the air 
there is highly electrified and repelled, the reaction pushing the 
wheel around like a Barker's mill or Hero's steam engine. Some- 
times the flyer is mounted with its axis horizontal and across the 
rails on a railroad along which it travels. 

Synonym — Reaction Wheel. 

Foci Magnetic. The two points on the earth's surface where the 
magnetic intensity is greatest. They nearly coincide in position 
with the magnetic poles. 

Fog, Electric. Fogs occurring when the atmosphere is at 
unusually high potential and accompanied by frequent change of 
such polarity. 

Following Horns. In dynamo-electric machines the projecting 
ends of the pole pieces towards which the outer uncovered peri- 
meter of the armature turns in its regular operations. The leading 
horns are those away from which the armature rotates. In consid- 
ering rotation the exposed portion of the superficies of the arma- 
ture is considered. The definition would have to be reversed if 
the part facing the pole pieces were considered. 

Synonym — Trailing Horns. 

Foot=candle. A unit of illuminating power ; the light given by 
one standard candle at a distance of one foot. The ordinary units 
of illuminating power are entirely relative ; this is definite. It is 
due to Carl Herring. 

Foot=pOund. A practical unit of work or energy. The quan- 
tity of work required to raise a pound one foot, or one hundred 
pounds one-hundredth of a foot, and so on ; or the potential energy 
represented by a weight at an elevation under these conditions. 

Foot=step. In a dynamo with armature at the lower end of 
its field magnets, the plate generally of zinc, interposed between it 
and the iron base plate to prevent the leakage of lines of force 
outside of the circuit. Any dia-magnetic material which is 
mechanically suitable may be used. 

Force. Force may be variously defined, {a) Any cause of 
change of the condition of matter with respect to motion or rest. 
(b) A measurable action upon a body under which the state of 
rest of that body, or its state of uniform motion in a straight line, 



2 6o STANDARD ELECTRICAL DICTIONARY. 

suffers change, (c) It may be defined by its measurement as the 
rate of change of momentum, or (d) as the rate at which work is 
done per unit of space traversed. 

Force is measured by the acceleration or change of motion it 
can impart to a body of unit mass in a unit of time, or, calling force, 
F, — mass, m — and acceleration per second a — we have F = m a. 

The dimensions of force are mass (M) X acceleration (L/T 2 ) = 
ML/T 2 . 

Force de Cheval. Horse power (French). It is the French or 
metric horse power. 
It is equal to : 

542.496 Foot lbs. per second. 

.9864 English Horse Power. 

75 Kilogram-meters per second. 

Force, Electro=magnetic. The mechanical force of attraction or 
repulsion acting on the electro-magnetic unit of quantity. Its 
intensity varies with the square of the distance. It may also be 
denned as electric force in the electro-magnetic system. 

Its dimensions are equal to mechanical force (ML,/T 2 ) divided by 
quantity (M*I,*) = M^/T 2 . 

Force, Electrostatic. The force by which electric matter or 
electrified surfaces attract or repel each other. It is also termed 
electric force (not good) and electro-motive intensity. It is the 
mechanical force acting upon a unit quantity of electricity. Its 
intensity varies with the square of the distance. 

Its dimensions are therefore equal to (quantity X unity (-f- 
(square of distance) Q. Xi -+ L 2 = M*L S /T Xi -f V = M*I>/T 
These dimensions are also those of potential difference. 

The objection to the term electric force is that it may be applied 
also to electro-magnetic force, and hence be a source of confusion. 

Forces, Parallelogram of. The usual method of composing 
forces or resolving a force. The sides of a parallelogram of forces 
represent component forces and the diagonal represents the result- 
ant. See Component — Resultant — Forces, Composition of—Forces, 
Resolution of 

Forces, Composition of. When several forces act in a different 
direction upon a point they may be drawn or graphically repre- 
sented as arrows or lines emanating from the point in the proper 
direction and of lengths proportional to the force they exercise. 
Any two can be treated as contiguous sides of a parallelogram and 
the parallelogram can be completed. Then its diagonal, called the 
resultant, will represent the combined action of the two forces, 



STANDARD ELECTRICAL DICTIONARY. 261 

both as regards direction and intensity. This is the composition 
of two forces. 

If more than two forces act upon the given point the resultant 
can be composed with any of the others and a new force 
developed. The new resultant can be combined with another 
force, and the process kept up, eliminating the components 
one by one until a final resultant of all is obtained. This 
will give the exact direction and intensity of the forces, however 
many or varied. 

Forces, Resolution of. The developing from a single force 
treated as a resultant, two other forces in any desired direction. The 
reverse of composition of forces. (See Forces, Composition of— 
Forces, Parallelogram of— Components — Resultant.) 

Force, Tubes of. Aggregations of lines of force, either electrostatic 
or magnetic. They generally have a truncated, conical or pyra- 
midal shape and are not hollow. Every cross-section contains the 
same number of lines. The name it will seem is not very expressive. 

Force, Unit of. The fundamental or or C. G. S. unit of force is 
the dyne, q. v. 

The British unit of force is the poundal (the force which will 
produce an acceleration of one foot per second in a mass of one 
pound). It is equal to about -^ pound. A force cannot be 
expressed accurately in weight units, because weight varies with 
the latitude. 

Forming. The process of producing secondary battery plates 
from lead plates by passing a charging current through the cell 
alternately in opposite directions, and discharging the cell after 
each charge. See (Battery, Secondary, Planters.) 

Foundation Ring. In a dynamo armature the ring-shaped core 
on which Gramme ring armatures and other ring armatures are 
wound. 

Fourth State of Matter. Gas so rarefied that its molecules do 
not collide, or rarely do so; radiant matter, q. v. 

Frame. In a dynamo the bed-piece is sometimes called the 
frame. 

Franklin's Experiment. Franklin proved the identity of light- 
ning and electricity by flying a kite in a thunder storm. The kite 
was of silk so as to endure the wetting. When the string became 
wet sparks could be taken from a key attached to its end. The 
main string was of hemp ; at the lower end was a length of silk to 
insulate it. The key was attached near the end of and to the hemp 
string. 




262 STANDARD ELECTRICAL DICTIONARY. 

Franklin's Plate. A simple form of condenser. It consists of 
a plate of glass coated on each side with tinfoil with a margin of 

about an inch of clear glass. One 
coating may be grounded as indi- 
cated in the cut, and the plate 
charged like a Ley den jar. Or one 
side may be connected with one 
terminal, and the other with the other 
terminal of an influence machine and 
the pane will be thus charged. 
Synonym — Fulminating Pane. 

Franklin's Theory. The single 
fluid theory, q. v., of electricity. 
Fig. i 74 . Franklin's Plate. Frequency. The number of double 

reversals or complete alternations per second in an alternating 
current. 

Synonym — Periodicity. 

Frictional Electricity. Electricity produced by friction of 
dissimilar substances. (See Electrostatic Series.) The contact 
theory holds that friction plays only a secondary role in this 
process ; that it increases the thoroughness of contact, and tends 
to dry the rubbing surfaces, but that the charges induced are due 
to contact of dissimilar substances, not to friction of one against 
the other. 

Frictional Heating. The heating of a conductor by the passage 
of a current ; the Joule effect, q. v. 

Fringe. The outlying edge of a magnetic field. 

Frog, Galvani's Experiment With. A classic experiment in 
electricity, leading to the discovery of current or dynamic electric- 
ity. If a pair of legs of a recently killed frog are prepared with 
the lumbar nerves exposed near the base of the spinal column, and 
if a metallic conductor, one half-length zinc and the other half- 
length copper, is held, one end between the lumbar nerves and the 
spine, and the other end against one of the muscles of the thigh or 
lower legs, the moment contact occurs and the circuit is completed 
through the animal substance the muscles contract and the leg is 
violently drawn upwards. Galvani, in 1786, first performed, by 
accident, this famous experiment, it is said, with a scalpel with 
which he was dissecting the animal. He gave his attention to the 
nerves and muscles. Volta, more happily, gave his attention to 
the metals and invented the voltaic battery, described by him in 
a letter to Sir Joseph Banks, dated 1800. 

Frog, Rheoscopic. If the nerve or living muscle of a frog is 



STANDARD ELECTRICAL DICTIONARY. 



263 



suddenly dropped upon another living muscle so as to come in 
contact with its longitudinal and transverse sections, the first 
muscle will contract on account of the stimulation of its nerve due 
to the passage of a current derived from the second muscle (Ganot). 
The experiment goes under the above title. 

Frying. A term applied to a noise sometimes produced in 
a voltaic arc due to too close approach of the carbons to each 
other. It has been suggested that it may be due to volatilization 
of the carbon. (Elihu Thomson.) 

Fulgurite. An irregular and tubular mass of vitrified quartz, 
believed to be formed by melting under the lightning stroke. 




Fig". 1 7S- Crucible, Electric. 

Furnace, Electric. A furnace in which the heat is produced by 
the electric current. It has hitherto been practically used only in 
the extraction of aluminum and silicium from their ores. The 
general principle involves the formation of an arc between carbon 
electrodes. The substances to be treated are exposed to the heat 
thus produced. Sometimes the substances in the arc form 
imperfect conductors, and incandescence takes a part in the action. 
Sometimes the substances are merely dropped through the arc. 

Fuse Board. A tablet on which a number of safety fuses are 
mounted. Slate is excellent material for the tablet, as it is incom- 
bustible, and is easily drilled and worked. 

Fuse Box. A box containing a 
safety fuse. Porcelain is an excellent 
material for its base. No combustible 
material should enter into its composi- 
tion. 

Fuse, Cockburn. A safety fuse or 
cut off which consists of a wire of pure 
tin running from terminal to terminal, 
to whose centre a leaden ball is secured FiR C ockburn Safety Fuse. 

by being cast into position. The con- 
nection with the terminals is made by rings at the ends of the wire 
through which the terminal screws are passed and screwed home. 




264 



STANDARD ELECTRICAL DICTIONARY. 



When the tin softens under too heavy a current the weight of the 
shot pulls it apart. 

Fuse, Electric. A fuse for igniting an explosive by electricity. 

There are two kinds. In one a thin wire unites the ends of the 

two conducting wires as they enter the case of the fuse. The 



*> 





Fig. 177. Electric Fuse. 

larger wires are secured to the case, so that no strain comes on the 
fine wire. On passing a current of sufficient strength the small 
wire is heated. In use the fuse is bedded in powder, which again 
may be surrounded by fulminating powder, all contained in a 
copper or other metallic case. Such a detonator is used for explod- 
ing gun-cotton and other high explosives. 

The other kind of fuse is similar, but has no thin connecting 
wire. The ends of the conductors are brought nearer together 
without touching. In use a static discharge is produced across 
from end to end of the conductors, igniting a proper explosive 
placed there as in the other case. 

The first kind of fuse is generally operated by a battery or small 
mechanical generator — the latter by a spark coil, frictional or influ- 
ence machine or by a Leyden jar. 

Galvanic, adj. Voltaic ; relating to current electricity or the 
electrolytic and electro- chemical relations of metals. (For titles in 
general under this head see Voltaic — or the main title.) 

Galvanic Element. A galvanic couple with exciting fluid and 
adjuncts ; a galvanic cell. The word element is sometimes applied 
to the electrodes of a cell, as the carbon element or zinc element. 



STANDARD ELECTRICAL DICTIONARY. 265 

Galvanic Polarization. The polarization of a voltaic couple. 
(See Polarization.) » 

Galvanism. The science of voltaic or current electricity. 

Galvanization, (a) Electroplating or depositing a metal over 
the surface of another by electrolysis. 

(&) In medical electricity the effects produced on any part of the 
system by the current of voltaic battery. Various descriptive 
qualifications are prefixed, such as " general" galvanization, indi- 
cating its application as applied to the whole body, " local" for the 
reverse case, and so on. 

Galvanization, Labile. Application of the galvanic current in 
electro-therapeutics where one sponge electrode is employed which 
is rubbed or moved over the body, the other being in constant con- 
tact with the body. 

Galvanized Iron. Iron coated with zinc by cleaning and 
immersion in melted zinc. The iron is prevented from rusting by 
galvanic action. It forms the negative element in a couple of 
which the zinc is the positive element. From this electric protec- 
tive action the name is derived. 

Galvano=cautery, Chemical. Electro-therapeutic treatment 
with sharp electrodes, one of which is inserted in the tissue and 
a current passed by completing the circuit through the tissue so as 
to electrolyze or decompose the fluids of the tissue. It is applied 
in the removal of hair or extirpation of the follicle. The process 
is not one of heating, and is improperly named cautery. 

Galvano=faradization. In medical electricity the application 
of the voltaic and induced or secondary current simultaneously 
to any part of the system. 

" Galvanometer. An instrument for measuring current strength 
and sometimes for measuring inferentially potential difference, 
depending on the action of a magnetic field established by the 
current, such action being exerted on a magnetic needle or its 
equivalent. 

A current passing through a conductor establishes circular 
lines of force. A magnetic needle placed in their field is acted on 
and tends to place itself parallel with the lines, in accordance with 
the principles of current induction. (See Induction, Electro- 
magnetic.) A common compass held near a conductor through 
which a current is passing tends to place itself at right angles to 
such conductor. For a maximum effect the conductor or the part 
nearest the needle should lie in the magnetic meridian. If at 
right angles thereto its action will only strengthen the directive 
force of the earth's induction or magnetic field, as the needle 



266 



STANDARD ELECTRICAL DICTIONARY. 



naturally points north and south. Such combination is virtually a 
galvanometer. 

A typical galvanometer comprises a flat coil of wire placed 
horizontally within which a magnetic needle is delicately poised, so 
as to be free to rotate with the least possible friction. The needle 
may be supported on a sharp point like a compass needle, or may 
be suspended by a long fine filament. It should be covered by a 
glass plate and box, or by a glass shade. Finally a graduated disc 
may be arranged to show the amount of deflection of the needle. 

In use the apparatus is turned about until the needle, as acted on 
by the earth's magnetic field, lies parallel to the direction of the 
coils of wire. On passing a current through the coil the needle is 
deflected, more or less, according to its strength. 

By using exceedingly fine wire, long enough to give high resist- 
ance, the instrument can be used for very high potentials, or is in 
condition for use in determining voltage. By using a coil of 
large wire and low resistance it can be employed in determining 
amperage. In either case the deflection is produced by the current. 
The needle is often placed above or below the coil so as only to 
receive a portion of its effect, enough for all practical purposes in 
the commoner class of instruments. 

The galvanometer was invented by Schweigger a short time after 
Oersted's discovery, q. v. 

Galvanometer, Absolute. A galvanometer giving absolute 
readings ; properly one whose law of calibration can be deduced 
from its construction. Thus the diameter of the coil, and the con- 
stants and position of a magnetic needle suspended in its field 
being known, the current intensity required to deflect the needle a 
given number of degrees could be calculated. 
Galvanometer, Aperiodic. A galvanometer whose needle is 
damped (see Damping) as, for instance, 
by the proximity of a plate of metal, by 
an air vane or otherwise, so that it reaches 
its reading with hardly any oscillation. 
A very light needle and a strong magnetic 
field also conduce to vibrations of short 
period dying out very quickly. Such gal- 
vanometers are termed ' ' dead-beat. ' ' No 
instrument is absolutely dead-beat, only 
relatively so. 

Galvanometer, Astatic. A galvan- 
ometer with a pair of magnetic needles 

Fig. 178. Astatic connected astatically, or parallel with 

Galvanometer. . . -v.. r A , , . 

their poles 111 opposition. (See Astatic 

Needle.) Each needle has its own coil, the coils being wound in 




STANDARD ELECTRICAL DICTIONARY. 



267 



opposite directions so as to unite in producing deflections in the 
same sense. As there should be some directive tendency this is 
obtained by one of the magnets being slightly stronger than the 
other or by the proximity of a fixed and adjustable controlling 
magnet, placed nearer one needle than the other. 

For small deflections the currents producing them are propor- 
tional to their extent. 

Galvanometer, Ballistic. A galvanometer whose deflected 
element has considerable moment of inertia ; the exact opposite of 
an aperiodic or dead beat galvanometer. (See Galvanometer, 
Aperiodic, ) All damping by air vanes or otherwise must be care- 
fully done away with. 




Fig. 179. Siemens & Halske's Galvanometer. 

Siemens & Halske's galvanometer is of the reflecting or mirror 
type (see Galvanometer, Reflecting} with suspended, bell-shaped 
magnet, in place of the ordinary magnetic needle, or astatic com- 
bination of the lightest possible weight in the regular instrument. 



268 STANDARD ELECTRICAL DICTIONARY. 

A copper ball drilled out to admit the magnet is used as damper 
in the ordinary use of the instrument. To convert it into a ballistic 
galvanometer the copper ball is removed. The heavy suspended 
magnet then by its inertia introduces the desired element into the 
instrument. 

Referring to the cut, Fig. 179, Mis the suspended magnet, with 
north and south poles n and 5 ; S is the reflecting mirror ; r is the 
tube containing the suspending thread ; K is the damper removed 
for ballistic work. 

The ballistic galvanometer is used to measure quantities of 

electricity in an instantaneous discharge, which discharge should 

be completed before the heavy needle begins to move. The extreme 

elongation or throw of the needle is observed, and depends (1) on 

the number of coulombs (K) that pass during the discharge ; (2) on 

the moment of inertia of the needle and attached parts ; (3) on the 

moment of the controlling forces, i. e. , the forces tending to pull 

the needle back to zero ; (4) on the moment of the damping forces ; 

(5) on the moment of the deflecting forces due to a given constant 

P k° 

current. The formula is thus expressed : K = — X A X sin — 



tan a° 
in which K = coulombs discharged ; P = periodic time of vibra- 
tion of needle ; A = amperes producing a steady deflection 
equal to a° ; k° = first angular deflection of needle. For accuracy 
k° and a° should both be small and the damping so slight as to be 
negligible. Otherwise a correction for the latter must be applied. 
For approximate work for k° and a° the deflections read on the scale 
may be used with the following formula : K = P/tf X A/2 X k°\a. 

Galvanometer Constant. Assume a galvanometer with a very 
short needle and so placed with respect to its coils that the mag- 
netic field produced by a current circulating in them is sensibly 
uniform in the neighborhood of the needle, with its lines of force 
at right angles thereto. The field is proportional to the current i> 
so that it may be denoted by G i. Then G is the galvanometer 
constant. If now the angle of deflection of the needle is 9 against 
the earth's field H, M being the magnetic moment of the needle 
we have G i M cos = H M sin Q or i = H/G tan G. H/G is the 
reduction factor ; variable as H varies for different places. 

For a tangent galvanometer the constant G is equal to itc nja y in 
which n denotes the number of turns of wire, and a denotes the 
radius of the circle. 

Galvanometer, Differential. A galvanometer in which the 
needle is acted on by two coils wound in opposition, each of equal 
deflecting action and of equal resistance. If a current is divided 
between two branches or parallel conductors, each including one 
of the coils, when the needle points to zero the resistances of the 



STANDARD ELECTRICAL DICTIONARY. 



269 



two branches will be equal. In the cut, C C represent the coils, 
and A and B the two leads into which the circuit, P Q, is divided. 




Fig. 59. 
Fig. 180. Theory of Differential Galvanometer. 

Galvanometer, Direct Reading. A calibrated galvanometer, 
whose scale is graduated by volts or amperes, instead of degrees. 

Galvanometer, Marine. (Sir 

William Thomson's.) A galvanom- 
eter of the reflecting type, for 
use on shipboard. A fibre suspen- 
sion is adopted for the needle. The 
fibre is attached to a fixed support 
at one end and to a spring at the 
other, and the needle is suspended 
by its centre of gravity. This 
secures it to a considerable extent 
from disturbance due to the roll- 
ing of the ship. A thick iron box 
encloses the needle, etc., to cutoff 
any magnetic action from the 
ship. (See Galvanometer, Reflect- 
ing.) 

Galvanometer, Potential. A 

galvanometer wound with fine 
German silver wire to secure high 
resistance used for determination 
Of potential difference. Fig. 181. Differential Galvanometer. 

Galvanometer, Proportional. A galvanometer so constructed 
that the deflections of its index are proportional to the current 
passing. It is made by causing the deflecting force to increase 
as the needle is deflected, more and more, or by causing the 
restitutive force to diminish under like conditions, or by both. The 
condition is obtained in some cases by the shape and position of 
the deflecting coils. 

Galvanometer, Quantity. A galvanometer for determining 




270 



STANDARD ELECTRICAL DICTIONARY. 



quantities of electricity, by the deflections produced by discharging 
the quantities through their coils. It is a ballistic galvanometer 
with very little or no damping. 

Galvanometer, Reflecting. A galvanometer the deflections of 
whose needle are read by an image projected by light reflected from 




Fig. 183. Reflecting Galvanometer. 

a mirror attached to the needle or to a vertical wire carrying the 
needle. A lamp is placed in front of the instrument facing the 
mirror. The light of the lamp is reflected by the mirror upon a 
horizontal scale above the lamp. An image of a slit or of a wire 
may be caused thus to fall upon the scale, the mirror being slightly 
concave, or a lens being used to produce the projection. 



STANDARD ELECTRICAL DICTIONARY. 



If the mirror swings through a horizontal arc, the reflected 
image will move, in virtue of a simple geometrical principle, 
through an arc of twice as many degrees. The scale can be 
placed far from the mirror, so that the ray of light will represent 
a weightless index of very great length, and minute deflections of 
the needle will be shown distinctly upon the scale. 

In the cut, Fig. 182, the ray of light from the lamp passes 
through the aperture, m m, and is made parallel by the lens, L. 
At 5 is the mirror attached to the needle and moving with it. A 
scale placed at t receives the reflection from the mirror. The cut, 
Fig. 183, shows one form of the instrument set up for use. 

Synonym — Mirror Galvanometer. 

Galvanometer Shunt. To prevent too much current passing 
through a galvanometer (for fear of injury to its insulation) a shunt 




Fig. 184. Sine Galvanometer. 

is sometimes placed in parallel with it. The total current will be 

distributed between galvanometer and shunt in the inverse ratio of 

their respective resistances. (See Multiplying Power of a Shunt.) 

Galvanometer, Sine. A galvanometer whose measurements 



272 STANDARD ELECTRICAL DICTIONARY. 

depend upon the sine of the angle of deflection produced when the 
coil and needle lie in the same vertical plane. 

The needle, which may be a long one, is surrounded by a coil, 
which can be rotated about a vertical axis passing through the 
point of suspension of the needle. Starting with the needle at rest 
in the plane of the coil, a current is passed through the coil 
deflecting the needle, the coil is swung around deflecting the 
needle still more, until the needle lies in the plane of the coil ; the 
intensity of the current will then be in proportion to the sine of the 
angle through which the coil and needle move. 

In the galvanometer M is a circle carrying the coil, N is a scale 
over which the needles, m and n, move, the former being a mag- 
netic needle, the latter an index at right angles and attached 
thereto ; a and b are wires carrying the current to be measured. 
The circles, M and N y are carried by a base, O, around which they 
rotate. H is a fixed horizontal graduated circle. In use the circle, 
My is placed in the magnetic meridian, the current is passed 
through the coil, M ; the needle is deflected ; M is turned until its 
plane coincides with the direction of the needle, m. The current 




Fig". 185. Tangent Galvanometer. 

strength is proportional to the sine of the angle of deflection. 
This angle is measured by the vernier, C, on the circle, H, The 
knob, Ay is used to turn the circle, M. 
Galvanometer, Tangent. A galvanometer in which the tan- 



STANDARD ELECTRICAL DICTIONARY. 



273 



gents of the angles of deflection are proportional to the currents 
producing such deflections. 

For this law to apply the instrument in general must fulfill the 
following conditions : (1) The needle must be controlled by a uni- 
form magnetic field such as that of the earth ; (2) the diameter of 
the coil must be large compared to the length of the needle ; (3) 
the centre of suspension of the needle must be at the centre of the 
coil ; (4) the magnetic axis of the needle must lie in the plane of 
the coil when no current is passing. 

If a single current strength is to be measured the best results will 
be attained when the deflection is 45 ° ; in comparing two currents 
the best results will be attained when the deflections as nearly as 
possible are at equal distances on both sides of 45 . 

The needle should not exceed in length one-tenth the diameter 
of the coil. 

For very small deflections any galvanometer follows the law of 
tangential deflection. 

As for very small deflections the tangents are practically equal to 
the arcs subtended, for such de- 
flections the currents are propor- 
tional to the deflections they 
produce. 

The sensibility is directly pro- 
portional to the number of con- 
volutions of wire and inversely 
proportional to their diameter. 

The tangent law is most ac- 
curately fulfilled when the depth 
of the coil in the radial direction 
is to the breadth in the axial 
direction as \/ 2> '. 1/2, or about 
as 11:9. 

Galvanometer, Torsion. A 

galvanometer whose needle is 

suspended by a long filament or 

by a thread and spiral spring 

against whose force of torsion 

the movements of the needle are 

produced. The current strength 

is determined by bringing the 

needle back to its position of rest 

by turning a hand-button or other arrangement. The angle through 

which this is turned gives the angle of torsion . From this the current 

strength is calculated on the general basis that it is proportional to 

the angle of torsion. 




Fig. 186. Torsion Galvanometer. 



274 



STANDARD ELECTRICAL DICTIONARY. 



Galvanometer, Vertical. A galvanometer whose needle is 
mounted on a horizontal axis and is deflected in a vertical plane. 
One of the poles is weighted to keep it normally vertical, repre- 
senting the control. It is not used for accurate work. 

Synonym — Upright Galvanometer. 

Galvanometer, Volt= and 
Ampere=meter. A galvanom- 
eter of Sir William Thom- 
son's invention embodying the 
tangent principle, and having its 
sensibility adjustable by moving 
the magnetic needle horizontally 
along a scale (the " meter") 
towards or away from the coil. A 
curved magnet is used to adjust 
the control. The leads are 
twisted to prevent induction. 

The instrument is made with 
a high resistance coil for voltage 
determinations, and with a low 
resistance coil for amperage de- 
terminations. 

Fig. 187. Vertical Galvanometer. At one end of a long base 

board a vertical coil with its 
plane at right angles to the axis of the board is mounted. A scale 
(the * ' meter ' ' of the name) runs down the centre of the board. A 
groove also runs down the centre. The magnetic needle is con- 
tained in a quadrant-shaped glass-covered box which slides up and 





Fig. 188. Sir William Thomson's Ampere-meter Galvanometer. 

down the groove. A number of short parallel needles mounted 
together, with an aluminum pointer are used. 

In the cut P is the base board, M is a glass covered case contain- 



STANDARD ELECTRICAL DICTIONARY. 275 

ing the magnetic needle, and sliding along the base board, being 
guided by the central groove, C, is the coil. Between the coil and 
the needle is the arched or bent controlling magnet. The long 
twisted connecting wires are seen on the right hand. 

Galvano=plastics. The deposition of metals by electrolysis, a 
disused term replaced by electro-deposition, electroplating, and 
electro-metallurgy. 

Galvano=puncture. An operation in medical electricity. (See 
Electro-puncture. ) 

Galvanoscope. An instrument, generally of the galvanometer 
type, used for ascertaining whether a current is flowing or not. 
Any galvanoscope, when calibrated, if susceptible thereof, becomes 
a galvanometer. 

Gas, Electrolytic. Gas produced by the decomposition, gener- 
ally of water, by electrolysis. It may be hydrogen or oxygen, or a 
mixture of the two, according to how it is collected. (See Gases, 
Mixed.) 

Gases, Mixed. The mixture of approximately one volume of 
oxygen and two volumes of hydrogen collected in the eudiometer 
of a gas voltameter or other electrolytic apparatus. 

Gassing. The evolution of gas from the plates of a storage 
battery in the charging process, due to too high voltage in the 
circuit of the charging dynamo. 

Gastroscope. An apparatus for illuminating by an incan- 
descent lamp the interior of the stomach, and with prisms to 
refract the rays of light so that the part can be seen. The stomach 
is inflated with air, if desirable, to give a better view. An incan- 
descent platinum spiral in a water jacket has been employed for 
the illumination. 

Gassiot's Cascade. A goblet lined for half its interior surface 
with tinfoil. It is placed in the receiver of an air pump from the 
top of whose bell a conductor descends into it, not touching the 
foil. On producing a good rarefaction, and discharging high 
tension electricity from between the conductor just mentioned and 
the metal of the machine, a luminous effect is produced, as if the 
electricity, pale blue in color, was overflowing the goblet. 

Gauss. A name suggested for unit intensity of magnetic field. 
Sylvanus P. Thomson proposed for its ^alue the intensity of a 
field of io 8 C. G. S. electro-magnetic units. J. A. Fleming 
proposed the strength of field which would develop one volt 
potential difference in a wire io 6 centimeters long, moving through 
such field with a velocity of one centimeter per second. This is 



276 



STANDARD ELECTRICAL DICTIONARY. 



one hundred times greater than Thomson's standard. Sir William 
Thomson suggested the intensity of field produced by a current 
of one ampere at a distance of one centimeter 

Gauss' Principle. An electric circuit acts upon a magnetic pole 
in such a way as to make the number of lines of force that pass 
through the circuit a maximum. 




JiM: 



... d ~ 



Fig. 189. Gauss' Tangent Position. 



Gauss, Tangent Positions of. The " end on " and " broadside " 
methods of determining magnetization involve positions which 

have been thus termed. (See 
Broadside Method and End on 
Method.) 

Gear, Magnetic Friction. 

Friction gear in which the com- 
ponent wheels are pressed 
against each other by electro- 
magnetic action. In the cut, 
repeated from Adherence, Elec- 
tro-magnetic, the magnetizing 
coil makes the wheels, which are 
of iron, press strongly together. 

Geissler Tubes. Sealed tubes 
of glass containing highly rare- 
fied gases, and provided with 
platinum electrodes extending 
through the glass tightly sealed 
as they pass through it, and often 
Fig. 190. Magnetic Friction Gear. extending a short distance be- 
yond its interior surface. 
On passing through them the static discharge luminous effects 




STANDARD ELECTRICAL. DICTIONARY. 277 

are produced varying with the degree of exhaustion, the contents 
(gas), the glass itself, or solutions surrounding it. The two latter 
conditions involve fluorescence phenomena often of a very beautiful 
description. 

The pressure of the gas is less than one-half of a millimeter of 
mercury. If a complete vacuum is produced the discharge will 
not pass. If too high rarefaction is produced radiant matter 
phenomena (see matter, Radiant) occur. 

Geissler tubes have been used for lighting purposes as in mines, 
or for illuminating the interior cavities of the body in surgical or 
medical operations. 

Generating Plate. The positive plate in a voltaic couple, or 
the plate which is dissolved ; generally a plate of zinc. 
Synonyms — Positive Plate — Positive Element. 

Generator, Current. Any apparatus for maintaining an elec- 
tric current. It may be as regards the form of energy it converts 
into electrical energy, mechanical, as a magneto or dynamo elec- 
tric machine or generator ; thermal, as a thermo-electric battery ; 
or chemical, as a voltaic battery ; all of which may be consulted. 

Generator, Secondary. A secondary or storage battery. (See 
Battery y Secondary.) 

German Silver. An alloy of copper, 2 parts, nickel, 1 part, and 
zinc, 1 part. Owing to its high resistance and moderate cost and 
small variation in resistance with change of temperature, it is much 
used for resistances. From Dr. Mathiessen's experiment the 
following constants are deduced in legal ohms : 

Relative Resistance (Silver = i), 13-92 

Specific Resistance at o° C. (32F.), 20.93 microhms. 

Resistance of a wire, 

(a) 1 foot long, weighing 1 grain, 2.622 ohms. 

1 foot long, 1-1000 inch thick, 125.91 " 

1 meter long, weighing 1 gram, 1.830 " 

1 meter long, 1 millimeter thick, 0.2666 " 

Resistance of a 1 inch cube at o°C. (32 F.), 8.240 microhms. 

Approximate percentage increase of resistance pero° C. (i.8° F.) 
at about 20 C. (68° F.), 0.044 per cent. 

Gilding, Electro=. The deposition of gold by an electric current, 
or electrolytically in the electroplating bath. 

Gilding Metal. A special kind of brass, with a high percentage 
of copper, used to make objects which are to be gilded by elec- 
trolysis. 



278 



STANDARD ELECTRICAL DICTIONARY. 



Gimbals. A suspension used for ships' compasses and some- 
times for other apparatus. It consists of a ring held by two 
journals, so as to be free to swing in one plane. The compass 
is swung upon this ring, being placed concentrically therewith. 
Its journals are at right angles to those of the ring. This gives a 
universal joint by which the compass, weighted below its line of 
support, is always kept horizontal. 




Fig. 191. Compass Suspended in Gimbals. 

Glass. A fused mixture of silicates of various oxides. It is of 
extremely varied composition and its electric constants vary greatly. 
Many determinations of its specific resistance have been made. 
For flint glass at ioo° C. (212 F.) about 206 X io 12 ohms — at 
6o° C (140 F.) 1020 X io 12 (Thomas Gray) is given, while another 
observer (Beetz) gives for glass at ordinary temperatures an immeas- 
urably high resistance. It is therefore a non-conductor of very 
high order if dry. As atlielectric the specific inductive capacity of 
different samples of flint glass is given as 6.57 — 6.85 — 7.4 — 10. 1 
(Hopkinson), thus exceeding all other ordinary dielectrics. The 
densest glass, other things being equal, has the highest specific 
inductive capacity. 

Gold. A metal, one of the elements; symbol Au.c; atomic 
weight, 196.8; equivalent, 65.6 ; valency, 3; specific gravity 19.5. 
It is a conductor of electricity. 

Annealed. Hard drawn. 

Relative Resistance (Annealed Silver =1), 1.369 1-393 



Specific Resistance, 

Resistance of a wire at o° C. (32°F.) 

(a) 1 foot long, weighing 1 grain, 

(b) 1 foot long, 1-1000 inch thick, 

(c) 1 meter long, weighing 1 gram, 

(d) 1 meter long, 1 millimeter thick, 



2.058 



2.094 



57.85 
12.38 


58.84 

12.60 


•4035 

.02620 


.4104 
.02668 



ohms 



STANDARD ELECTRICAL DICTIONARY. 



279 



Annealed. Hard drawn. 
Resistance of a 1 inch cube at o° C.(32° F.) .8102 .8247 

Approximate increase in resistance pero°C, (i.8° F) at about 
20 C. (68° F.), 0.365 per cent. 
Electro-chemical equivalent (Hydrogen == .0105), .6888 

Gold Bath. A solution of gold used for depositing the metal 
in the electroplating process. 

A great number of formulae have been devised, of which a few 
representative ones are given here. 





COLD BATHS. 


HOT BATHS. 


Water, 


10,000 


10,000 


IO,000 


IO,000 


5,000 


3,000 


Potassium Cyanide, 


200 





200 


IO 





50 


Gold,- 


IOO 


15 


IOO 


IO 


IO 


IO 


Potass. Ferrocyanide, 





200 








150 





Potassium Carbonate, 





I50 


. 





50 





Ammonium Chloride, 





30 








20 





Aqua Ammoniae, 







500 











Sodium Phosphate, - 











600 








Sodium Bisulphite, - 











IOO 









(Roseleur.) 
In the baths the gold is added in the form of neutral chloride, 
Auric chloride (Au Cl 6 ). 

Gold Stripping Bath. A bath for removing gold from plated 
articles without dissolving the base in order to save the precious 
metal. A bath of 10 parts of potassium cyanide and 100 parts of water 
may be used, the articles to be stripped being immersed therein as the 
anode of an active circuit. If the gilding is on a silver or copper 
basis, or on an alloy of these metals the same solution attacks the 
base and dissolves it, which is objectionable. For silver articles it 
is enough to heat to cherry red and throw into dilute sulphuric 
acid. The gold scales off in metallic spangles. For copper 
articles, a mixture of 10 volumes concentrated sulphuric acid, 1 
volume nitric acid, and 2 volumes hydrochloric acid may be 
used by immersion only, or with a battery. The sulphuric acid 
in such large excess is supposed to protect the copper. For copper 
articles concentrated sulphuric acid alone with the battery may be 
used. This does not sensibly attack the copper if it is not allowed to 
become diluted. Even the dampness of the air may act to dilute it. 

Graduator. Apparatus for enabling the same line to be used for 
telegraph signals and telephoning. 

One type consists in coils with iron cores or simply electro- 
magnets. These act to retard the current in reaching its full power 



28o STANDARD ELECTRICAL DICTIONARY. 

and also prolong it. This gives a graduated effect to the signals, 
so that the telephone diaphragm is not audibly affected by the 
impulses. 

The telephoning current is so slight and so rapid in its character- 
istic changes that it is without effect upon the ordinary telegraph. 

Gram. The unit of weight in the metric system ; accepted as 
the unit of mass in the absolute of C. G. S. system of units. It is 
the one-thousandth part of mass of a standard weight preserved under 
proper conditions in Paris, and supposed to be the mass of a cubic 
decimeter of distilled water at the temperature of the maximum 
density of water. The standard is the kilogram ; the temperature 
is 3. 9 C. (39 F.). The standard kilogram is found to be not 
exactly the weight of a cubic decimeter of water, the latter weigh- 
ing 1. 0000 1 3 kilogram. 

If therefore the denned gram on the water basis is taken as the 
unit it varies very slightly from the accepted gram. 

1 gram is equal to 15.43234874 grains. (Prof. W. H. Miller.) 

Gram=atom. The number of grams of an element equal numeric- 
ally to the atomic weight, as 16 grams of oxygen, 1 gram of 
hydrogen, 35.5 grams of chlorine ; all which might be expressed as 
gram-atoms of oxygen, hydrogen and chlorine respectively. 

The gram-atom approximately expresses the number of gram- 
calories required to heat one gram of the substance i° C. (i.8° F.). 
This is in virtue of Dulong and Petri's discovery that the atomic 
weight of an element multiplied by its specific heat gives approxi- 
mately a constant for all elements. 

Gram=molecule. The number of grams of a substance equal 
numerically to its molecular weight. 

Graphite. Carbon ; one of three allotropic modifications of this 
element. It occurs in nature as a mineral. 

It is used as a lubricant for machinery ; for commutator brushes ; 
for making surfaces to be plated conductive, and for mixing with 
manganese binoxide in Leclanche' cells. 

Gravitation. A natural force which causes all masses of matter 
to attract each other. Its cause is unknown ; it is often supposed 
to be due to the luminiferous ether. 

Gravity, Acceleration of. The velocity imparted to a body in 
one second by the action of gravitation at any standard point upon 
the earth's surface in a vacuum. This will vary at different places, 
owing principally to the variation in centrifugal force due to the 
earth's rotation. For standard valuation it must be reduced to sea 
level. The following are examples of its variation : 



STANDARD ELECTRICAL DICTIONARY. 281 

Equator, 978.1028 centimeters per second 

Paris, 980.94 " " " 

Greenwich 981.17 " " " 

Edinburgh, 981.54 " " " 

Pole (N. or S.), 983.1084 (theoretical) " " " 

As round numbers for approximate calculations 981 centimeters 

or 32.2 feet may be employed. 

Gravity, Control. Control by weight. In some ammeters and 

voltmeters gravity is the controlling force. 

Grid. A lead plate perforated or ridged for use in a storage 
batter}- as the supporter of the active materials and in part as con- 
tributing thereto from its own substance. 

Ground. The contact of a conductor of an electric circuit with 
the earth, permitting the escape of current if another ground exists. 

Ground=wire. A metaphorical term applied to the earth when 
used as a return circuit. 

Grove's Gas Battery. A voltaic battery depending for its action 
on the oxidation of hydrogen instead of the oxidation of zinc. Its 
action is more particularly described under Battery \ Gas. In the 




Fig. 758. 



Fig. 192. Grove's Gas Battery. 
cut B, B 1 , * * * are the terminals of the positive or hydrogen 
electrodes, marked H, and A t A 1 * * * are the terminals of the 
negative or oxygen electrodes marked O, while M, M l , " :( ~ * ~ is 
dilute sulphuric acid. 



282 



STANDARD ELECTRICAL DICTIONARY. 



Guard Ring. An annular horizontal surface surrounding the 
balanced disc in the absolute electrometer. (See Electrometer ; 
Absolute,) 

Guard Tube, A metal tube surrounding a dry pile used with a 
quadrant electrometer, or other electrometers of that type. It 
prevents the capacity of the lower brass end of the pile (which brass 
end closes the glass tube containing the discs) from momentary 
change by approach of some conductor connected to the earth. 
There are other guard tubes also. 

Gun, Electro=magnetic. An electro-magnet with tubular core. 
If, when it is excited a piece of an iron rod is pushed into the central 
aperture of the core and is released, the magnetic circle will try 
to complete itself by pushing the rod out so that it can thus be 
discharged, as if from a popgun. 

Synonym — Electric Popgun. 




Fig. 193. "Electric Popgun." 

Gutta Percha. The hardened milky juice of a tree, the 
Isonandra gutta, growing in Malacca and other parts of the 
Eastern Archipelago. It is much used as an insulator or constit- 
uent of insulators. 

Resistance after several minutes electrification per 1 centimeter 
cube at 54 C. (75 F.), 45°Xio 12 ohms. 

The specific resistance varies — from 25X10 12 to 500 Xio 12 ohms. 
A usual specification is 200 Xio 12 ohms. The influence of tem- 
perature on its resistance is given in Clark & Bright's empirical 
formula, R=R #*> in which R is the resistance at temperature 
t° C— R the resistance at o° C (32 F), a is the coefficient .8944. 

The resistance increases with the time of passage of the current, 
the variation being less the higher the temperature. 



STANDARD ELECTRICAL DICTIONARY. 283 

Time of Electrification. 



1 n 


11m 


2 


i < 


5 


(< 


10 


< i 


20 


a 


30 
£0 





Relative Resistance 


Relative Resistance 


at o° C (32 


F.) 


at 


24 


C 


(75° F.) 


100 










5-5i 


127.9 










6. 


163. 1 










6.66 


190.9 










6.94 


230.8 










7.38 


250.6 










7-44 


290.4 










7.6 


318.3 










7.66 



In cable testing one minute is generally taken as the time of 
electrification. 

Pressure increases the resistance by the formula R p=K (i-f- 
.00327^) in which R/> is the resistance at pressure/ — R resistance 
at atmospheric pressure—/ pressure in atmospheres. Thus in the 
ocean at a depth of 4,000 meters (2.4855 miles), the resistance is 
more than doubled. The longer the pressure is applied, the 
greater is the resistance. 

The specific inductive capacity of gutta percha is 4.2. 

Good gutta percha should not break when struck with a hammer, 
should recover its shape slowly, and it should support much more 
than 300 times its own weight. 

Gyrostatic Action of Armatures. Owing to gyrostatic action 
a rotating armature resists any change of direction of its axis. On 
ships and in railway motors which have to turn curves this action 
occurs. A 148 lb. armature running at 1,300 revolutions per 
minute may press with 30 lbs. on each journal as the ship rolls 
through an angle of 20 in 16 seconds. 

H. (a) The symbol for the horizontal component of the earth's 
magnetization. 

(b) The symbol for the intensity of a magnetizing force or field. 
The symbol H, as it is generally used, may mean either the number 
of dynes which act upon a unit pole, or the number of lines of force 
per centimeter. 

(c) The symbol for the unit of self-induction. 

Hair, Removal of, by Electrolysis. A method of depilation 
by destruction of individual hair follicles by electrolysis. 

A fine platinum electrode is thrust into a hair follicle. It is the 
negative electrode. The positive electrode is in contact with the 
body of the person under treatment ; it is often a sponge electrode 
simply held in his hand. A current of two to four milliamperes 
from an E. M. F. of 15 to 20 volts, is passed. This destroys the 
follicle, the hair is removed and never grows again. A gradual 



284 STANDARD ELECTRICAL DICTIONARY. 

increase of current is advised for the face. As only one hair is 
removed at once, but a small number are taken out at a sitting. 

Haldat's Figures. With a pole of a strong bar magnet, used 
like a pencil, imaginary figures are drawn upon a hard steel plate, 
such as a saw-blade. The pattern is gone over several times. By 
dusting iron filings on a sheet of paper laid over the steel plate, 
while horizontal, very complicated magnetic figures are produced. 

Hall's Experiment. A cross of thin metal, such as gold leaf, is 
secured upon a pane of glass. To two opposite arms a battery is 
connected in circuit with them. To the other two arms a galva- 
nometer is connected in circuit. If the cross is put into a field of 
force whose lines are perpendicular thereto, the galvanometer will 
disclose a constant current. The current is pushed, as it were, into 
the galvanometer circuit. Other metals have been used with 
similar results. They must be thin or the experiment fails. If the 
arm receiving the battery current is horizontal, and if it flows from 
left to right, and if the lines of force go from downward through 
the cross, the current in the galvanometer circuit will flow from 
the observer through the other arms of the cross, if the cross is of gold, 
silver, platinum or tin, and the reverse if of iron. The experiment 
has indicated a possible way of reaching the velocity of electricity 
in absolute measure. 

Hall Effect. The effect observed in Hall's experiment, q. v. 

Hall Effect, Real. A transverse electro-motive force in a con- 
ductor through which a current is passing produced by a magnetic 
field. 

Hall Effect, Spurious. A spurious electro-motive force pro- 
duced in a conductor, through which a current is passing by changes 
in conductivity of the conductor brought about by a magnetic field. 

Hanger Board. A board containing two terminals, a suspending 
hook, and a switch, so that an arc lamp can be introduced into a 
circuit thereby, or can be removed as desired. 

Harmonic Receiver. A receiver containing a vibrating reed, 
acted on by an electro-magnet. Such a reed answers only to 
impulses tuned to its own pitch. If such are received from the mag- 
net it will vibrate. Impulses not in tune with it will not affect it. 
(See Telegraphy Harmonic.) 

Head Bath, Electric. A fanciful name for an electro-medical 
treatment of the head. The patient is insulated by an insulating 
stool or otherwise. His person is connected with one terminal of 
an influence machine. An insulated metallic circle, with points 
of metal projecting inward or downward, is placed about the head. 



STANDARD ELECTRICAL DICTIONARY. 285 

The circle is connected with the other pole of the machine. On 
working it a silent or brnsh discharge with air convection streams 
occurs between the patient's head and the circle of points. 

Head=Iight, Electric. An electric head-light for locomotives has 
been experimented with. It includes the parabolic reflection of 
the regular light with an arc-lamp in place of the oil lamp. An 
incandescent lamp may be used in the same place, but has no 
great advantage over oil as regards illuminating power. 

Heat. A form of kinetic energy, due to a confused oscillatory 
movement of the molecules of a body. Heat is not motion, as a 
heated body does not change its place ; it is not momentum, but it 
is the energy of motion. If the quantity of molecular motion is 
doubled the momentum of the molecules is also doubled, but the 
molecular mechanical energy or heat is quadrupled. 

As a form of energy it is measured by thermal units. The calorie 
is the most important, and unfortunately the same term applies to 
two units, the gram-degree C. and the kilogram-degree C. (See 
Calorie.) Calories are determined by a calorimeter, q. v. 

Independent of quantity of heat a body may be hotter or colder. 
Thermometers are used to determine its temperature. 

Heat is transmitted by conduction, a body conducting it slowly 
for some distance through its own substance. Bodies vary greatly 
in their conductivity for heat. It is also transmitted by convec- 
tion of gases or liquids, when the heated molecules traveling 
through the mass impart their heat to other parts. Finally it is 
transmitted by ether waves with probably the speed of light. This 
mode of transmission and the phenomena of it were attributed to 
radiant heat. As a scientific term this is now dropped by many 
scientists. This practice very properly restricts the term "heat" 
to kinetic molecular motion. 

The mechanical equivalent of heat is the number of units of work 
which the energy of one unit quantity of heat represents. (See 
Equivalents, Mechanical and Physical.) 

Heat, Atomic. The product of the specific heat of an element 
by its atomic weight. The product is approximately the same for 
all the elements, and varies as determined between 5.39 and 6.87. 
The variations are by some attributed principally to imperfection 
of the work in determining them. The atomic heat represents the 
number of gram calories required to raise the temperature of a 
gram atom (a number of grams equal numerically to the atomic 
weight) one degree centigrade. 

Heat, Electric. This term has been given to the heat produced 



286 STANDARD ELECTRICAL DICTIONARY. 

by the passage of a current of electricity through a conductor. It 
is really electrically produced heat, the above term being a 
misnomer. 

The rise of temperature produced in a cylindrical conductor by 
a current depends upon the diameter of the conductor and on the 
current. The length of the wire has only the indirect connection 
that the current will depend upon the resistance and consequently 
upon its length. 

The quantity of heat produced in a conductor by a current is in 
gram-degree C. units equal to the product of the current, by the 
electro-motive force or potential difference maintained between the 
ends of the wire, by .24. 

The cube of the diameter of a wire for a given rise of tempera- 
ture produced in such conductor by a current is equal approxi- 
mately to the product of the square of the current, by the specific 
resistance (q. v.) of the material of the conductor, by .000391, the 
whole divided by the desired temperature in centigrade units. 

Heat, Electrical Convection of. A term applied to the 
phenomena included under the Thomson effect, q. v., the unequal 
or differential heating effect produced by a current of electricity in 
conductors whose different parts are maintained at different tem- 
peratures. 

Heater, Electric. An apparatus for converting electrical 
energy into thermal energy. 

An incandescent lamp represents the principle, and in the Edison 
meter has been used as such to maintain the temperature of the 
solutions. Heaters for warming water and other purposes have 
been constructed, utilizing conductors heated by the passage of the 
current as a source of heat. (See also Heating Magnet.) 

Heating Error. In voltmeters the error due to alteration of 
resistance of the coil by heating. If too strong a current is sent 
through the instrument, the coils become heated and their resist- 
ance increased. They then do not pass as much current as they 
should for the potential difference to which they may be exposed. 
Their readings then will be too low. One way of avoiding the 
trouble is to have a key in circuit, and to pass only an instanta- 
neous or very brief current through the instrument and thus get 
the reading before the coils have time to heat. 

The heating error does not exist for ammeters, as they are con- 
structed to receive the entire current, and any heating ' ' error ' ' 
within their range is allowed for in the dividing of the scale. 

Heating Magnet. An electro-magnet designed to be heated by 
Foucault currents induced in its core by varying currents in the 



STANDARD ELECTRICAL DICTIONARY. 287 

windings. It has been proposed as a source of artificial heat, a 
species of electric heating apparatus for warming water, or other 
purposes. 

Heat, Irreversible, The heat produced by an electric current 
in a conductor of identical qualities and temperature throughout. 
Such heat is the same whatever the direction of the current. The 
heating effect is irreversible because of the absence of the Thomson 
effect, q. v., or Peltier effect, q. v. 

Heat, Mechanical Equivalent of. The mechanical energy cor- 
responding to a given quantity of heat energy. Mechanical energy 
is generally represented by some unit of weight and height, such 
as the foot-pound ; and heat energy is represented by a given 
weight of water heated a given amount, such as a pound-degree 
centigrade. Joule's equivalent is usually accepted ; it states that 
772.55 footpounds of mechanical energy are equivalent to 1 pound- 
degree F. (one pound avds. of water raised in temperature one 
degree Fahrenheit). Other equivalencies have also been deduced. 

Heat, Molecular. The product of a specific heat of the compound 
by its molecular weight. It is approximately equal to the sum of 
the atomic heats of its constituent elements. 

The molecular heat represents the number of gram calories 
required to raise the temperature of a gram-molecule (a number of 
grams equal numerically to the molecular weight) one degree centi- 
grade. 

The molecular heat is approximately equal for all substances. 

Heat, Specific. The capacity of a body for heat ; a coefficient 
representing the relative quantity of heat required to raise the tem- 
perature of an identical weight of a given body a defined and 
identical amount. 

The standard of comparison is water ; its specific heat is taken as 
unity. The specific heats by weight of other substances are less 
than unity. The specific heat varies with the temperature. Thus 
the specific heat of water is more strictly i+. 00015 ^° C. 

Specific heat is greater when a substance is in the liquid than 
when it is in the solid state. Thus the specific heat of ice is 0.489 ; 
less than half that of water. It differs with the allotropic modifica- 
tions of bodies; the specific heat of graphite is. 202; of diamond, .147. 

The product of the specific heat by the atomic weight of 
elements gives a figure approximately the same. A similar law 
applies in the case of molecules. (See Heat, Atomic — Heat, 
Molecular.) 

The true specific heat of a substance should be separated from 
the heat expended in expanding a body against molecular and 



288 



STANDARD ELECTRICAL DICTIONARY. 



atomic forces, and against the atmospheric pressure. So far this 
separation has not been possible to introduce in any calculations. 

Heat, Specific, of Electricity., A proposed term to account for 
the heat absorbed or given out in unhomogeneous conductors, by 
the Thomson effect, or Peltier effect (see Effect, Thomson — Effect, 
Peltier.) If a current of electricity be assumed to exist, then 
under the action of these effects it may be regarded as absorbing or 
giving out so many coulombs of heat, and thus establishing a basis 
for specific heat. 

Heat Units. The British unit of heat is the pound degree F — 
the quantity of heat required to raise the temperature of a pound 
of water from 32 to 33 F. 

The C. G. S. unit is the gram-degree C. ; another metric unit is 
the kilogram-degree C. The latter is the calorie ; the former is 
sometimes called the small calorie or the joule ; the latter is some- 
times called the large calorie. The term joule is also applied to a 
quantity of heat equivalent to the energy of a watt-second or volt- 
coulomb. This is equal to .241 gram degree calorie. 

Hecto. A prefix to terms of measurement — meaning one hun- 
dred times, as hectometer, one hundred meters. 

Heliograph. An apparatus for reflecting flashes of light to a 
distant observer. By using the Morse telegraph code messages 
may thus be transmitted long distances. When possible the sun's 
light is used. 

Helix. A coil of wire ; properly a coil wound so as to follow the 
outlines of a screw without overlaying itself. 



.: : 1 v . . = ._;■'-. :.. ■: .- .■ - .;■ -. = - ■■<■ - :■ -■ .:.: . 



Fig. 194. Left-handed Helix. 



Fig. 195. Right-handed Helix. 

Henry. The practical unit of electro-magnetic or magnetic 
inductance. It is equal to io 9 C. G. S., or absolute units of induc- 
tance. As the dimensions of inductance are a length the henry is 
equal to io 9 centimeters, or approximately to one quadrant of the 
earth measured on the meridian. 

Synonyms— Secohm— Quadrant— Quad. 



STANDARD ELECTRICAL DICTIONARY. 



289 



Hermetically Sealed. Closed absolutely tight. Glass vessels, 
such as the bulbs of incandescent lamps, are hermetically sealed 
often by melting the glass together over any opening into their 
interior. 

Heterostatic Method. A method of using the absolute or 
attracted disc electrometer. (See Electrometer Absolute.) The for- 
mula for its idiostatic use, q. v., involves the determination of d, 
the distance between the suspended and fixed discs. As this is 
difficult to determine the suspended disc and guard ring may be 
kept at one potential and the lower fixed disc is then connected 
successively with the two points whose potential difference is to be 
determined. Their difference is determined by the difference 
between d and d / ', the tw T o distances between the discs. This dif- 
ference is the distance through w^hich the micrometer screw is 

moved. The heterostatic formula is : 

V — V = (d / — d) y 7 8 it F 



High Frequency. 



in which V and V' are potentials of the two points ; d / and d the 
two distances between the discs necessary for equilibrium ; S the 
area of the disc and F the force of attraction in dynes. (See 
Idiostatic Method.) 

High Bars of Commutator. Commutator bars, which in the 
natural wear of the commutator, project beyond the others. The 
surface then requires turning down, as it should be quite cylin- 
drical. 

A term used as a noun or as an adjective to 
indicate in an alternating current, the pro- 
duction of a very great number of alterna- 
tions per unit of time — usually expressed as 
alternations per second. 

Hissing. A term applied to a noise some- 
times produced by a voltaic arc ; probably 
due to the same cause as frying, q. v. 

Hittorf 's Solution. A solution used as a 
resistance. It is a solution of cadmium 
iodide in amylic alcohol. Ten per cent, of 
the salt is used. It is contained in a tube 
with metallic cadmium electrodes. (See 
Resistance, Hittorf s.) 

Holders, (a) The adjustable clamps for 
holding the armature brushes of dynamos 
and motors. 
(b) The clamps for holding the carbons of arc lamps. 




Fig. 196. Hittorf's Re 
sistance Tube. 



290 STANDARD KIvECTRICAI, DICTIONARY. 

(c) The clamps for holding safety fuses, q. v. 

(d) Holders for JablochkofF candles and other electric candles. 
(See. Candle Holders.) 

(e) A box or block of porcelain for holding safety fuses. 

Hood. A tin hood placed over an arc-lamp. Such hoods are. 
often truncated cones in shape, with the small end upwards. They 
reflect a certain amount of light besides protecting the lamp to 
some extent from rain. 

Horns. The extensions of the pole pieces of a dynamo or motor. 
(See Following Horns — Leading Horns. ) 
Synonym — Pole Tips. 

Horse Power. A unit of rate of work or activity. There are 
two horse powers. 

The British horse power is equal to 33,000 pounds raised one 
foot per minute, or 550 footpounds per second, or 1. 0138 metric 
horse power. 

The metric horse power (French) is equal to 75 kilogram-meters, 
or 542 foot pounds per second, or .986356 British horse power. 

H. P. is the abbreviation for horse power. (See Horse Power, 
Electric.) 

Horse Power, Actual. The rate of activity of a machine, as 
actually developed in condition for use. It is less than the indi- 
cated or total horse power, because diminished by the hurtful resist- 
ances of friction, and other sources of waste. It is the horse power 
that can be used in practise, and which in the case of a motor can 
be taken from the fly-wheel. 

Horse Power, Electric. The equivalent of a mechanical horse 
power in electric units, generally in volt-amperes or watts ; 745.943 
watts are equivalent to the activity of one British horse power ; 
735.75 are equivalent to one metric horse power. The number 
746 is usually taken in practical calculations to give the equiva- 
lency. 

Horse Power, Indicated. The horse power of an engine as 
indicated by its steam pressure, length of stroke, and piston area, and 
vacuum, without making any deduction for friction or hurtful 
resistances. The steam pressure is in accurate work deduced from 
indicator diagrams. 

Horse Power, Hour. A horse power exerted for one hour, or 
the equivalent thereof. As the horse power is a unit of activity, 
the horse power hour is a unit of work or of energy. It is equal 
to 1,980,000 foot pounds. 

H. P. Abbreviation for " horse power " 



STANDARD ELECTRICAL DICTIONARY. 



291 



Hughes' Electro=magnet. A horseshoe electro-magnet with 
polarized core. It is made by mounting two bobbins of insulated 
wire on the ends of a permanent horse- 
shoe magnet. It was devised for use in 
Hughes' printing telegraph, where very 
quick action is required. The contact 
lasts only .053 second, 185 letters being 
transmitted per minute. 

Hughes' Induction Balance. An ap- 
paratus for determining the presence of 
a concealed mass of metal. The apparatus 
is variously connected. The cut shows a 
representative form ; a and a' are two 
primary coils, each consisting of 100 
meters (328 feet) of No. 32 silk covered 
copper wire (0.009 inch diameter) wound Fi g"- 1 97> 
on a boxwood spool % inches in depth ; 
b and b f are secondary coils. All coils 
are supposed to be alike. The primary coils are joined in series 
with a battery of three or four Daniell cells. A microphone m is 




Hughes' Electro- 
magnet. 




Fig. 198. Hughes' Induction Balance. 

included in the same circuit. The secondary coils are joined in 
series with a telephone and in opposition with each other. The 



292 STANDARD ELECTRICAL DICTIONARY. 

clock is used to produce a sound affecting the microphone. If all 
is exactly balanced there will be no sound produced in the tele- 
phone. This balance is brought about by slightly varying the distance 
of one of the secondaries from the primary, until there is no sound 
in the telephone. If now a piece of metal is placed within either 
of the coils, it disturbs the balance and the telephone sounds. 

To measure the forces acting a sonometer or audiometer is used. 
This is shown in the upper part of the cut. Two fixed coils, c and 
e are mounted at the ends of a graduated bar. A movable coil dis 
connected in the telephone circuit ; c and e by a switch can be con- 
nected with the battery and microphone circuit, leaving out the 
induction balance coils. The ends of the coils c and e, facing each 
other are of the same polarity. If these coils, c and £, were equal in 
all respects, no sound would be produced when d was midway 
between them. But they are so wound that the zero position for d 
is very near one of them, c. 

Assume that a balance has been obtained in the induction bal- 
ance with the coil d at zero. No sound is heard whether the switch 
is moved to throw the current into one or the other circuit. A 
piece of metal placed in one of the balance coils will cause the pro- 
duction of a sound. The current is turned into the sonometer and 
d is moved until the same sound, as tested by rapid movements of 
the switch, is heard in both circuits. The displacement of d gives 
the value of the sound. 

A milligram of copper is enough to produce a loud sound. Two 
coins can be balanced against each other, and by rubbing one of 
them, or by breathing on one of them, the balance will be dis- 
turbed and a sound will be produced. 

Prof. Hughes has also dispensed with the audiometer. He has 
used a strip of zinc tapering from a width of 4 mm. (.16 inch) at one 
end to a sharp edge or point at the other. The piece to be tested 
being in place in one coil, the strip is moved across the face of the 
other until a balance is obtained. 

As possible uses the detection of counterfeit coins, the testing of 
metals for similarity of composition and the location of bullets 
in the body have been suggested. Care has to be taken that no 
masses of metal interfere. Thus in tests of the person of a 
wounded man, the presence of an iron truss, or of metallic bed 
springs may invalidate all conclusions. 

The same principle is carried out in an apparatus in which the 
parts are arranged like the members of a Wheatstone bridge. One 
pair of coils is used, which react on each other as primary and 
secondary coils. One of the coils is in series with a telephone in 
the member of the bridge corresponding to that containing the 



STANDARD ELECTRICAL DICTIONARY. 



293 



galvanometer of the Wheatstone bridge. The latter is more 
properly termed an induction bridge. 

Synonyms — Inductance Bridge — Inductance Balance — Induction 
Bridge. 

Hydro=electric. adj. (a) A current produced by a voltaic couple 
or the couple itself is sometimes thus characterized or designated, 
as a "hydro-electric current" or a "hydro-electric couple." It 
distinguishes them from thermo-electric. 

(6) Armstrong's steam boiler electric machine (see Hydro- 
electric Machine) is also termed a hydro-electric machine. 

Hydro=eIectric Machine. An apparatus for generating high 
potential difference by the escape of steam through proper nozzles. 

It consists of a boiler mounted on four glass legs or otherwise 
insulated. An escape pipe terminates in a series of outlets so 
shaped as to impede the escape of the steam by forcing it out of 
the direct course. These jets are lined with hard wood. They 
are enclosed in or led through a box which is filled with cold water. 




Fig. 199. Armstrong's Hydro-electric Machine. 

This is to partly condense the steam so as to get it into the vesicular 
state, which is found essential to its action. Dry steam produces 
no excitation. If the boiler is fired and the steam is permitted to 



294 STANDARD ELECTRICAL DICTIONARY. 

escape under the above conditions the vesicles presumably, or the 
" steam " is found to be electrified. A collecting comb held against 
the jet becomes charged and charges any connected surface. 

The boiler in the above case is negatively and the escaping 
" steam " is positively charged. By changing the material of the 
linings of the jets, or by adding turpentine the sign of the elec- 
tricity is reversed. If the water contains acid or salts no electricity 
is produced. The regular hydro-electric machine is due to Sir 
William Armstrong. 

Faraday obtained similar results with moist air currents. 

Hydrogen. An element existing under all except the most 
extreme artificial conditions of pressure and cold as a gas. It is 
the lightest of known substances. Atomic weight, i ; molecular 
weight, 2; equivalent, 1 ; valency, 1 ; specific gravity, .0691 — .0695. 
(Dumas & Boussingault.) 

It is a dielectric of about the same resistance as air. Its specific 
inductive capacity at atmospheric pressure is : 
•9997 (Baltzman) 
.9998 (Ayrton) 

Electro-chemical equivalent, .0105 milligram. 

The above is usually taken as correct. Other values are as 
follows : 

.010521 (Kohllrausch) 
.010415 (Mascart) 
The electro-chemical equivalent of any element is obtained by 
multiplying its equivalent by the electro-chemical equivalent of 
hydrogen. The value .0105 has been used throughout this book. 

Hygrometer. An instrument for determining the moisture in the 
air. One form consists of a pair of thermometers, one of which 
has its bulb wrapped in cloth which is kept moist during the obser- 
vation. The evaporation is more or less rapid according to the 
dryness or moisture of the air, and as the temperature varies with 
this evaporation the relative readings of the two thermometers 
give the basis for calculating the hygrometric state of the air. 
Another form determines the temperature at which dew is deposited 
on a silver surface, whence the calculations are made. 

Hysteresis, Magnetic. A phenomenon of magnetization of 
iron. It may be attributed to a sort of internal or molecular 
friction, causing energy to be absorbed when iron is magnetized. 
Whenever therefore the polarity or direction of magnetization of a 
mass of iron is rapidly changed a considerable expenditure of energy 
is required. It is attributed to the work done in bringing the 
molecules into the position of polarity. 



STANDARD ELECTRICAL DICTIONARY. 295 

The electric energy lost by hysteresis may be reduced by vibra 
tions or jarring imparted to the iron, thus virtually substituting 
mechanical for electrical work. 

On account of hysteresis the induced magnetization of a piece of 
iron or steel for fields of low intensity will depend on the manner 
in which the material has been already magnetized. Let the 
intensity of field increase, the magnetization increasing also ; then 
lower the intensity ; the substance tends to and does retain some of 
its magnetism. Then on again strengthening the field it will have 
something to build on, so that when it attains its former intensity 
the magnetization will exceed its former value. For a moderate 
value of intensity of field the magnetization can have many values 
within certain limits. 

Synonym — Hysteresis — Hysteresis, Static — Magnetic Friction. 

Hysteresis, Viscous. The gradual increase or creeping up of 
magnetization when a magnetic force is applied with absolute 
steadiness to a piece of iron. It may last for half an hour or more 
and amount to several per cent, of the total magnetization. It is 
a true magnetic lag. 

I. A symbol sometimes used to indicate current intensity. Thus 
Ohm's law is often expressed I = E R, meaning current intensity is 
equal to electro-motive force divided by resistance. C is the more 
general symbol for current intensity. 

Ideoelectrics or Isoelectrics. Bodies which become electric by 
friction. This was the old definition, the term originating with 
Gilbert. It was based on a misconception, as insulation is all that 
is requisite for frictional electrification, metals being thus electrified 
if held hy insulating handles. The term is virtually obsolete ; as 
far as it means anything it means insulating substances such as 
sealing wax, sulphur, or glass. 

Idle Coils. Coils in a dynamo, in which coils no electro-motive 
force is being generated. This may occur when, as a coil breaks 
connection with the commutator brush, it enters a region void of 
lines of magnetic force, or where the lines are tangential to the 
circle of the armature. 

Idiostatic Method. A method of using the absolute or attracted 
disc electrometer. ^See Electro meter, Absolute.) The suspended 
disc and guard ring are kept at the same potential, which is that of 
one of the points whose potential difference is to be determined ; 
the lower fixed disc is connected to the other of the points whose 
potential difference is to be determined. Then we have the formula 

! S it F 

V = d 

S 
in which d is the distance between the discs, V is the difference of 



296 STANDARD ELECTRICAL DICTIONARY. 

potential of the two points, F the force of attraction between the 
discs in dynes, and S the area of the suspended disc. (See Hetero- 
static Method.) 

Idle Poles. Poles of wire sealed into Crookes' tubes, not used 
for the discharge connections, but for experimental connections to 
test the effect of different excitation on the discharge. 

Idle Wire. In a dynamo the wire which plays no part in generat- 
ing electro-motive force. In a Gramme ring the wire on the inside 
of the ring is idle wire. 

Igniter. In arc lamps with fixed parallel carbons of the Jabloch- 
koff type (see Candle, Jablochkoff) a strip of carbon connects the 
ends of the carbons in the unused candle. This is necessary to 
start the current. Sucfi strip is called an igniter. It burns away 
in a very short time when an arc forms producing the light, and 
lasts, if all goes well, until the candle burns down to its end. With- 
out the igniter the current would not start and no arc would form. 

I. H. P. Symbol for indicated horse-power. 

Illuminating Power. The relative light given by any source 
compared with a standard light, and stated in terms of the same, as 
a burner giving an illuminating power of sixteen candles. For 
standards see Candle, Carcel — Methven Standard — Pentane Stand- 
ard. 

Illuminating Power, Spherical. The illuminating power of a 
lamp or source of light may vary in different directions, as in the 
case of a gas burner or incandescent lamp. The average illuminat- 
ing power determined by photometric test or by calculation in all 
directions from the source of light is called the spherical illuminat- 
ing power, or if stated in candles is called the spherical candle 
power. 

Illumination, Unit of. An absolute standard of light received by 
a surface. Preece proposed as such the light received from a stand- 
ard candle (see Candle, Standard) at a distance of 12.7 inches. 
The object of selecting this distance was to make it equal to the 
Carcel Standard (see Carcel) , which is the light given by a Carcel 
lamp at a distance of one meter. 

From one-tenth to one-fiftieth this degree of illumination was 
found in gas-lighted streets by Preece, depending on the proximity 
of the gas lamps. 

Image, Electric. An electrified point or system of points on 
one side of a surface which would produce on the other side of that 
surface the same electrical action which the actual electrification of 
that surface really does produce. (Maxwell.) 



STANDARD ELECTRICAL DICTIONARY. 297 

The method of investigating the distribution of electricity by 
electric images is due to Sir William Thomson. The conception is 
purely a theoretical one, and is of mathematical value and interest. 

Impedance. The ratio of any impressed electro-motive force to 
the current which it produces in a conductor. For steady currents 
it is only the resistance. For variable currents it may include 
besides resistance inductance and permittance. It is the sum of 
all factors opposing a current, both ohmic and spurious resistances. 
It is often determined and expressed as ohms. 

Synonym — Apparent Resistance — Virtual Resistance. 

Impedance, Oscillatory. The counter-electro-motive force 
offered to an oscillatory discharge, as that of a Leyden jar. It 
varies with the frequency of the discharge current. 

Synonym— Impulsive Impedance. 

Impressed Electro =motive Force. The electro-motive force 
expending itself in producing current induction in a neighboring 
circuit. 

Impulse. (a) An electro-magnetic impulse is the impulse 
produced upon the luminiferous ether by an oscillatory discharge 
or other varying type of current ; the impulse is supposed to be 
identical, except as regards wave-length, with a light wave. 

(b) An electro-motive impulse is the electro-motive force which rises 
so high as to produce an impulsive or oscillatory discharge, such as 
that of a Leyden jar. 

Incandescence, Electric. The heating 01 a conductor to red, 
or, more etymologically, to white heat by the passage of an elec- 
tric current. The practical conditions are a high intensity of 
current and alow degree of conductance of the conductor relatively 
speaking. 

Inclination Map. A map showing the locus of equal inclina- 
tion or dips of the magnetic needle. The map shows a series of 
lines, each one of which follows the places at which the dip of 
the magnetic needle is identical. The map changes from year to 
year. (See Magnetic Elements.) 

Independence of Currents in Parallel Circuits. If a number 
of parallel circuits of comparatively high resistance are supplied 
by a single generator of comparatively low resistance, the current 
passed through each one will be almost the same whether a single 
one or all are connected. Under the conditions named the 
currents are practically independent of each other. 

Indicating Bell. An electric bell arranged to drop a shutter or 
disclose in some other way a designating number or character 
when rung. 



298 STANDARD ELECTRICAL DICTIONARY. 

Indicator, (a) An apparatus for indicating the condition of a 
distant element, such as the water level in a reservoir, the tem- 
perature of a drying room or cold storage room or any other datum. 
They are of the most varied constructions. 

{b) The receiving instrument in a telegraph system is sometimes 
thus termed. 

Indicator, Circuit. A galvanometer used to show when a cir- 
cuit is active, and to give an approximate measurement of its 
strength. It is a less accurate and delicate form of instrument than 
the laboratory appliance. 

Inductance. The property of a circuit in virtue of which it 
exercises induction and develops lines of force. It is denned 
variously. As clear and satisfactory a definition as any is the fol- 
lowing, due to Sumpner and Fleming : Inductance is the ratio 
between the total induction through a circuit to the current pro- 
ducing it. ' ' Thus taking a simple helix of five turns carrying a 
current of two units, and assuming that 1,000 lines of force passed 
through the central turn, of which owing to leakage only 900 thread 
the next adjacent on each side, and again only 800 through the 
end turns, there would be 800 -f- 900 -f- 1000 -f- 900 -f- 800, or 4,400 
linkages of lines with the wire, and this being with 2 units of cur- 
rent, there would be 2,200 linkages with unit current, and conse- 
quently the self-inductance of the helix would be 2,200 centimetres. ' ' 
(Kennelly.) Inductance, as regards its dimensions is usually re- 
duced to a length, hence the last word of the preceding quotation. 

The practical unit of inductance is termed the henry, from Prof. 
Joseph Henry ; the secohm, or the quad or quadrant. The latter 
alludes to the quadrant of the earth, the value in length of the 
unit in question. 

Induction, Coefficient of Self. The coefficient of self-induc- 
tion of a circuit is the quantity of induction passing through it per 
unit current in it. If a given circuit is carrying a varying current 
it is producing a varying quantity of magnetic induction through 
itself. The quantity of induction through the circuit due to its 
current is generally proportional to its current. The quantity for 
unit current is the coefficient of self-induction. (Emtage.) 

Induction, Cross. The induction of magnetic lines of force in 
a dynamo armature core by the current passing around such arma- 
ture. These lines in a symmetrical two pole machine are at right 
angles to the lines of force which would normally extend across 
the space between the two magnet poles. The joint magnetizing 
effect of the field and of the cross induction produces a distorted 
field between the poles. 

Synonym — Cross-magnetizing Effect. 



STANDARD ELECTRICAL DICTIONARY. 299 

Induction, Electro=magnetic. The inter-reaction of electro- 
magnetic lines of force with the production of currents thereby. 

A current passing through a conductor establishes around it a 
field of force representing a series of circular lines of force concen- 
tric with the axis of the conductor and perpendicular thereto. 
These lines of force have attributed to them, as a representative of 
their polarity, direction. This is of course purely conventional. 
If one is supposed to be looking at the end of a section of con- 
ductor, assuming a current be passing through it towards the 
observer, the lines of force will have a direction opposite to the 
motion of the hands of a watch. The idea of direction may be 
referred to a magnet. In it the lines of force are assumed to go 
from the north pole through the air or other surrounding dielectric 
to the south pole. 

Two parallel wires having currents passing through them in the 
same direction will attract each other. This is because the oppositely 
directed segments of lines of force between the conductors destroy 
each other, and the resultant of the two circles is an approximation 
to an ellipse. As lines of force tend to be as short as possible the 
conductors tend to approach each other to make the ellipse become 
of as small area as possible, in other words to become a circle. 

If on the other hand the currents in the conductors are in oppo- 
site directions the segments of the lines of force between them will 
have similar directions, will, as it were, crowd the intervening 
ether and the wires will be repelled. 



/> 



/ 



/ / \ f~*-f — r . . if r 3 / 



Fig. 200. Attraction of Conductors Carrying Similar Currents. 

By Ampere's theory of magnetism, (see Magnetism, Ampere 's 
Theory of,) a magnet is assumed to be encircled by currents 
moving in the direction opposite to that of the hands of a watch 
as the observer faces the north pole. A magnet near a wire tends 
to place the Amp6rian currents parallel to the wire, and so that 
the portion of the Amperian currents nearest thereto will corre- 
spond in direction with the current in the wire. 



300 STANDARD ELECTRICAL DICTIONARY. 

This is the principle of the galvanometer. A number of 
methods oimemoria technica have been proposed to remember it by. 

Thus if we imagine a person swimming with the current and 
always facing the axis of the conductor, a magnetic needle held 
where the person is supposed to be will have its north pole deflected 
to the right hand of the person. 



I J ;\ } ■ i f I 






•><rss/ 



Fig. 201. Repulsion of Conductors Carrying Opposite Currents. 

Again if we think of a corkscrew, which as it is turned screws 
itself along with the current, the motion of the handle shows the 
direction of the lines of force and the direction in which the north 
pole of a needle is deflected. This much is perhaps more properly 
electro-dynamics, but is necessary as a basis for the expression of 
induction. 

If a current is varied in intensity in one conductor it will induce 
a temporary current in another conductor, part of which is parallel to 
the inducing current and which conductor is closed so as to form a 
circuit. If the inducing current is decreased the induced current 
in the near and parallel portion of the other circuit will be of 
identical direction ; if increased the induced current will be of 
opposite direction. 

This is easiest figured by thinking of the lines of force surround- 
ing the inducing conductor. If the current is decreased these can 
be imagined as receiving a twist or turn contrary to their normal 
direction, as thereby establishing a turn or twist in the ether surround- 
ing the other wire corresponding in direction with the direction 
of the original lines of force, or what is the same thing, opposite in 
direction to the the original twist. But we may assume that the 
establishment of such a disturbance causes a current, which must 
be governed in direction with the requirements of the new lines of 
forfce. 

The same reasoning applies to the opposite case. 

The general statement of a variable current acting on a neighbor- 
ing circuit also applies to the approach or recession of an unvary- 



STANDARD ELECTRICAL DICTIONARY. 301 

ing current, and to the cutting of lines of force by a conductor at 
right angles thereto. For it is evident that the case of a varying 
current is the case of a varying number of lines of force cutting or 
being cut by the neighboring conductor. As lines of force always 
imply a current, they always imply a direction of such current. 
The cutting of any lines of force by a closed conductor always 
implies a change of position with reference to all portions of such 
conductor and to the current and consequently an induced current 
or currents in one or the other direction in the moving conductor. 

As the inducing of a current represents energy abstracted from 
that of the inducing circuit, the direction of the induced current is 
determined by {Lenz's Law) the rule that the new current will 
increase already existing resistances or develop new ones to the 
disturbance of the inducing field. 

In saying that a conductor cutting lines of force at right angles 
to itself has a current induced in it, it must be understood that if 
not at right angles the right angle' component of the direction of 
the wire acts in generating the current. The case resolves itself 
into the number of lines of force cut at any angle by the moving 
wire. 

The lines of force may be produced by a magnet, permanent or 
electro. This introduces no new element. The magnet may be 
referred, as regards direction of its lines of force, to its encircling 
currents, actual or Amperian, and the application of the laws just 
cited will cover all cases. 

Induction, Coefficient of Mutual. The coefficient of mutual 
induction of two circuits is the quantity of magnetic induction 
passing through either of them per unit current in the other. 
(Emtage.) It is also denned as the work which must be done on 
either circuit, against the action of unit current in each, to take it 
away from its given position to an infinite distance from the 
other ; and also as the work which would be done by either circuit 
on the other in consequence of unit current in each, as the other 
moves from an infinite distance to its given position with respect 
to the other conductor. It depends on the form, size, and relative 
position of the two circuits ; and on the magnetic susceptibilities 
of neighboring substances. 

The ether surrounding two circuits of intensity i and i f must 
possess energy, expressible (Maxwell) as yi L i 2 -f- Mi i -\- % Ni 12 . 
It can be shown that M i i l in any given position of the two cir- 
cuits is numerically equal (1) to the mutual potential energy of 
the two circuits (2) to the number of lines of induction, which 
being due to A, pass from A through B, or equally being due to B, 
pass from B through A, and M is styled the coefficient of mutual 
induction. (Daniell.) 



3cxr STANDARD ELECTRICAL DICTIONARY. 

Induction, Electrostatic. An electrostatic charge has always 
an opposite and bound charge. This may be so distributed as not 
to be distinguishable, in which case the charge is termed, incor- 
rectly but conventionally, a free charge. But when a charge is 
produced an opposite and equal one always is formed, which is the 
bound charge. The region between the two charges and permeated 
by their lines of force, often curving out so as to embrace a volume 
of cross-sectional area larger than the mean facing area of the 
excited surfaces, is an electrostatic field of force. The establishing 
of an electrostatic field, and the production of a bound charge are 
electrostatic induction. 

An insulated conductor brought into such a field suffers a redis- 
tribution of its electricity, or undergoes electrostatic induction. 
The parts nearest respectively, the two loci of the original and the 
bound charges, are excited oppositely to such charges. The con- 
ductor presents two new bound charges, one referred to the original 
charge, the other to the first bound charge. 

Induction, Horizontal. In an iron or steel ship the induction 
exercised upon the compass needle by the horizontal members of 
the structure, such as deck-beams, when they are polarized by the 
earth's magnetic induction. This induction disappears four times 
in swinging a ship through a circle ; deviation due to it is termed 
quadrantal deviation. (See Deviation, Quadrantal.) 

Induction, Lateral. A term formerly used to express the 
phenomenon of the alternative discharge of a Ley den jar or other 
oscillatory discharge of electricity. (See Discharge, Alternative.) 

Induction, Magnetic. The magnetization of iron or other 
paramagnetic substance by a magnetic field. 

On account of its permeability or multiplying power for lines of 
force, a paramagnetic body always concentrates lines of force in 
itself if placed in a magnetic field, and hence becomes for the time 
being a magnet, or is said to be polarized. 

As the tendency of lines of force is to follow the most permeable 
path, a paramagnetic bar places itself lengthwise or parallel with the 
prevailing direction of the lines of force so as to carry them as 
far on their way as possible. Every other position of the bar is 
one of unstable equilibrium or of no equilibrium. The end of the 
bar where the lines of force enter (see Lines of Force) is a south 
pole and is attracted towards the north pole of the magnet. 

The production of magnetic poles under these conditions in the 
bar is shown by throwing iron filings upon it. They adhere to 
both ends but not to the middle. 

Induction, Mutual, Electro=magnetic. The induction due to 
two electric currents reacting on each other. 



STANDARD ELECTRICAL DICTIONARY. 303 

Induction, Mutual, Electrostatic. A charged body always 
induces a charge upon any other body near it ; and the same 
charge in the second body will induce the other charge in the first 
body if the latter isunexcited. In other words the second body's 
induction from the first is the measure of the charge the second 
would require to induce in the first its own (the second's) induced 
charge. This is the law of mutual electrostatic induction. 

Induction, Open Circuit. Inductive effects produced in open 
circuits. By oscillatory discharges a discharge can be produced 
across a break in a circuit otherwise complete. The requirements 
for its production involve a correspondence or relation of its dimen- 
sions to the inducing discharge. The whole is analogous to the 
phenomena of sound resonators and sympathetic vibrations. 

Synonym — Oscillatory induction. 

Induction, 5elf=. (a) A phenomenon of electric currents anal- 
ogous to the inertia of matter. Just as water which fills a pipe would 
resist a sudden change in its rate of motion, whether to start from 
rest, to cease or decrease its motion, so an electric current requires 
an appreciable time to start and stop. It is produced most strongly 
in a coiled conductor, especially if a core of iron is contained 
within it. 

As in the case of two parallel wires, one bearing currents 
which vary, momentary currents are induced in the other wire, so 
in a single condutor a species of inertia is found which retards and 
prolongs the current. If a single conductor is twisted into a 
helix or corresponding shape, its separate turns react one on 
the other in accordance with the general principles of electro- 
magnetic induction. (See Induction, Electro-magnetic.) Thus 
when a current is suddenly formed the coils acting upon each 
other retard for an instant its passage, producing the effect of a 
reverse induced current or extra current opposing the principal 
current. Of course no extra current is perceptible, but only the 
diminution. When the current is passing regularly and the cur- 
rent is broken, the corresponding action prolongs the current or 
rather intensifies itfor an instant, producing the true extra current. 
This is current self-induction. 

Synonyms — Electric Inertia — Electro-dynamic Capacity. 

(6) A permanent magnet is said to tend to repel its own magnet- 
ism, and thus to weaken itself; the tendency is due to magnetic 
self-induction. 

Induction Sheath. In the brush dynamo a thin sheet of cop- 
per surrounding the magnet cores with edges soldered together. 
The winding is outside of it. Its object is to absorb extra currents 
set up by variations in magnetic intensity in the cores. These 
currents otherwise would circulate in the cores. 



3°4 



STANDARD ELECTRICAL DICTIONARY. 



Induction, Unit of Self=. The unit of self-induction is the 
same as that of induction in general. It is the henry, q. v. 

Induction, Unipolar. Induction produced in a conductor which 
continuously cuts the lines of force issuing from one pole of a mag- 
net. As the lines of force are always cut in the same sense a con- 
tinuous and constant direction current is produced. 

Induction, Vertical. In an iron or steel ship the induction or 
attraction exercised in the compass by vertical elements of the 
structure. Such vertical masses of iron in the northern hemi- 
sphere would have their upper ends polarized as south poles, and 
would affect the magnet as soon as the vessel swung out of the mag- 
netic meridian. Thus this induction disappears twice in swing- 
ing a ship through a complete circle ; deviation due to it is termed 
semi-circular deviation. (See Deviation, Semi- circular.) 




Fig. 202. Inductor Dynamo. 

Inductophone. A method of train telegraphy. The train 
carries a circuit including a coil, and messages are picked up by it 
from coils along the line into which an alternating current is 
passed. A telephone is used as a receiver in place of a sounder 



STANDARD ELECTRICAL DICTIONARY. 305 

or relay. The invention, never practically used, is due to Wil- 
loughby Smith. 

Inductor, (a) In a current generator a mass of iron, generally 
laminated, which is moved past a magnet pole to increase the 
number of lines of force issuing therefrom. It is used in inductor 
dynamos. (See Dynamo Inductor.) In the cut Fig. 202, of an in- 
ductor dynamo i, i, are the laminated inductors. 

(b) In influence machines the paper or tinfoil armatures on which 
the electrification is induced. 

Inertia. A force in virtue of which every body persists in its 
state of motion or rest except so far as it is acted on by some force. 

Inertia, Electro=magnetic. This term is sometimes applied to 
the phenomena of self-induction, or rather to the cause of these 
phenomena. 

Infinity Plug. A plug in a resistance box, which on being 
pulled out of its seat opens the circuit or makes it of infinite resist- 
ance. The plug seats itself between two brass plates which are 
not connected with each other in any way. The other plates are 
connected by resistance coils of varying resistance. 

Influence, Electric. Electric induction, which may be either 
electrostatic, current, or electro-magnetic. 

Insolation, Electric. Exposure to powerful arc-light produces 
effects resembling those of sun-stroke. The above term or the 
term " electric sun-stroke" has been applied to them. 

Installation. The entire apparatus, buildings and appurtenances 
of a technical or manufacturing establishment. An electric light 
installation, for instance, would include the generating plant, any 
special buildings, the mains and lamps. 

Insulating Stool. A support for a person, used in experiments 
with static generators. It has ordinarily a wooden top and glass 
legs. It separates one standing on it from the earth and enables 
his surface to receive an electrostatic charge. This tends to make 
his hair stand on end, and any one on the floor who touches him 
will receive a shock. 

Insulating Tape. Prepared tape used in covering the ends of 
wire where stripped for making joints. After the stripped ends of 
two pieces are twisted together, and if necessary soldered and 
carefully cleaned of soldering fluid, they may be insulated by being 
wound with insulating tape. 

The tape is variously prepared. It may be common cotton or 
other tape saturated with any insulating compound, or may be a 
strip of gutta percha or of some flexible cement-like composition. 



306 STANDARD ELECTRICAL DICTIONARY. 

Insulating Varnish. Varnish used to coat the surface of glass 
electrical apparatus, to prevent the deposition of hygrometric 
moisture, and also in the construction of magnetizing and induc- 
tion coils and the like. Shellac dissolved in alcohol is much used. 
Gum copal dissolved in ether is another. A solution of sealiug 
wax in alcohol is also used. If applied in quantities these may 
need baking to bring about the last drying. (See Shellac Varnish,) 

Insulator, (a) Any insulating substance. 

(b) A telegraph or line insulator for telegraph wires. (See Insu- 
lator, Line or Telegraph.) 

Synonyms — Dielectric — Non-conductor. 

Insulator Cap. A covering or hood, generally of iron, placed 
over an insulator to protect it from injury by fracture with stones 
or missiles. 

Insulator, Fluid, (a) For very high potentials, as in induction 
coils or alternating circuits, fluid insulators, such as petroleum or 
resin oil, have been used. Their principal merit is that if a dis- 
charge does take place through them the opening at once closes, 
so that they are self-healing. 

(d) Also a form of telegraph or line insulator in which the lower 
rim is turned up and inwards, so as to form an annular cup which 
is filled with oil. 

Insulator, Line or Telegraph. A support often in the shape 
of a collar or cap, for a telegraph or other wire, made of insulating 
material. Glass is generally used in the United States, porcelain 
is adopted for special cases ; pottery or stone ware insulators have 
been used a great deal in other countries. Sometimes the insu- 
lator is an iron hook set into a glass screw, which is inserted into a 
hole in a telegraph bracket. Sometimes a hook is caused to depend 
from the interior of an inverted cup and the space between the 
shank of the hook and cup is filled with paraffine run in while 
melted. 

Insulators are tested by measuring their resistance while im- 
mersed in a vessel of water. 

Intensity. Strength. The intensity of a current or its amper- 
age or strength ; the intensity or strength of a magnetic field or its 
magnetic density ; the intensity or strength of a light are examples 
of its use. In the case of dynamic electricity it must be distin- 
guished from tension. The latter corresponds to potential differ- 
ence or voltage and is not an attribute of current ; intensity has no 
reference to potential and is a characteristic of current. 

Intensity of a Magnetic Field. The intensity of a magnetic 
field at any point is measured by the force with which it acts on a 



STANDARD ELECTRICAL DICTIONARY. 307 

unit magnet pole placed at that point. Hence unit intensity of 
field is that intensity of field which acts on a unit pole with a force 
of one dyne. (S. P. Thomson.) (See Magnetic Lines of Force.) 

Intercrossing. Crossing a pair of conductors of a metallic cir- 
cuit from side to side to avoid induction from outside sources. 

Intermittent. Acting at intervals, as an intermittent contact, 
earth, or grounding of a telegraph wire. 

Interpolar Conductor. A conductor connecting the two poles 
of a battery or current generator ; the external circuit in a galvanic 
circuit. 

Interpolation. A process used in getting a closer approxima- 
tion to the truth from two varying observations, as of a galvanom- 
eter. The process varies for different cases, but amounts to 
determining an average or deducing a proportional reading from 
the discrepant observed ones. 

Interrupter. A circuit breaker. It may be operated by hand 
or be automatic. (See Circuit Breaker — Circuit Breaker ■, Auto- 
matic — and others.) 

Interrupter, EIectro=magnetic, for a Tuning Fork. An appar- 
atus for interrupting a current which passes through an electro- 
magnet near and facing one of the limbs of a tuning fork. The 
circuit is made and broken by the vibrations of another tuning fork 
through which the current passes. The second one is thus made 
to vibrate, although it may be very far off and may not be in exact 
unison with the first. 

The first tuning fork has a contact point on one of its limbs, to 
close the circuit ; it may be one which dips into a mercury cup. 

Intrapolar Region. A term in medical electricity, denoting the 
part of a nerve through which a current is passing. 

Ions. The products of decomposition produced in any given 
electrolysis are termed ions, the one which appears at the anode 
or negative electrode is the anion. The electrode connected 
to the carbon or copper plate of a wet battery is an anode. Thus in 
the electrolysis of water oxygen is the anion and hydrogen is 
termed the kation. In this case both anion and kation are ele- 
ments. In the decomposition of copper sulphate the anion is 
properly speaking sulphion (S 4 ), a radical, and the kation is 
copper, an element. Electro-negative elements or radicals are anions, 
such as oxygen, sulphion, etc., while electro-positive ones are 
kations, such as potassium. Again one substance may be an anion 
referred to one below it and a kation referred to one above it, in 
the electro-chemical series, q. v. Anion means the ion which 



3 o8 STANDARD ELECTRICAL DICTIONARY. 

goes to the anode or positive electrode ; kation, the ion which goes 
to the kathode or negative electrode. 

Iron. A metal ; one of the elements ; symbol, Fe ; atomic 
weight, 56 ; equivalent, 28 and 14, ; valency, 4 and 2. It is a con- 
ductor of electricity. The following data are at o° C. 32 F. , with 
annealed metal. 

Specific Resistance, 9. 7 16 microhms. 

Relative Resistance, 6.460 

Resistance of a wire, 

(a) 1 foot long weighing 1 grain, 1.085 ohms. 

(b) 1 foot long 1 -1000 inch thick, 58.45 " 

(c) 1 meter long weighing 1 gram, »757o " 

(d) 1 meter long, 1 millimeter thick, .1237 " 
Percentage increase in resistance per degree C. i.8°F. at about 20 

C. (68°F.), about 0.5 per cent. 

Resistance of a 1 inch cube, 3.825 microhms. 

Electro-chemical equivalent (Hydrogen = .0105), .147 and .294 

Iron, Electrolytic. Iron deposited by electrolytic action. 
Various baths are employed for its formation. (See Steeling. ) It 
has very low coercive power, only seven to ten times that of nickel. 

Ironwork Fault of a Dynamo. A short circuiting of a dynamo 
by, or any connection of its coils with, the iron magnet cores or 
other iron parts. 

Isochronism. Equality of periodic time ; as of the times of 
successive beats of a tuning fork, or of the times of oscillations of 
a pendulum. 

Isoclinic Lines. The lines denoting the locus of sets of equal 
dips or inclinations of the magnetic needle upon the earth's sur- 
face, the magnetic parallels, q. v. These lines are very irregular. 
(See Magnetic Elements.) 

Isoclinic Map. A map showing the position of isoclinic lines. 

Isodynamic Lines. L,ines marking the locus of places of equal 
magnetic intensity on the earth's surface. (See Magnetic Ele- 
ments ; Poles of Intensity.) 

Isodynamic Map. A map showing the position of isodynamic 

lines. (See Poles of Intensity .) 

Isogonic Lines. Iyines on a map marking the locus of or con- 
necting those points where the declination or variation of the mag- 
netic needle is the same. (See Magnetic Elements — Declination 
of Magnetic Needle.) 

Synonyms — Isogonal L,ines — Halleyan Lines. 



STANDARD ELECTRICAL DICTIONARY. 309 

Isogonic Map. A map showing the isogonic lines. On such a 
map each line is characterized and marked with the degrees and 
direction of variation of the compass upon itself. 

Synonym — Declination Map. 

Isolated Plant, Distribution or Supply. The system of 
supplying electric energy by independent generating systems, 
dynamo or battery, for each house, factory or other place, as contra- 
distinguished from Central Station Distribution or Supply. 

Isotropic. (Grk. 160$ and rportoS, equal in manner.) Having equal 
properties in all directions ; the reverse of anisotropic, q. v. Thus 
a homogeneous mass of copper or silver has the same specific 
resistance in all directions and is an isotropic conductor. Glass 
has the same specific inductive capacity in all directions and is an 
isotropic medium or dielectric. The same applies to magnetism. 
Iron is an isotropic paramagnetic substance. (See Anisotropic.) 
The term applies to other branches of physics also. 

I. W. G. Contraction for Indian Wire Gauge — the gauge 
adopted in British India. 

J. Symbol for the unit joule, the unit of electric energy. 

Jacobi's Law. A law of electric motors. It states that the 
maximum work of a motor is performed when the counter-electro- 
motive force is equal to one-half the electro-motive force expended 
on the motor. 

Jewelry. Small incandescent lamps are sometimes mounted as 
articles of jewelry in scarf-pins or in the hair. Thevmay be supplied 
with current from storage or from portable batteries carried on the 
person. 

Joint, American Twist. A joint for connecting telegraph 
wires, especially aerial lines. Its construction is shown in the 
cut. The end of each wire is closely wound around the straight 
portion of the other wire for a few turns. 




Fig. 203. American Twist Joint. 

Joint, Britannia. A joint for uniting the ends of telegraph and 

electric wires. The ends of the wires are scraped clean and laid 

alongside each other for two inches, the extreme ends being bent 

up at about right angles to the wire. A thin wire is wound four 



3io 



STANDARD ELECTRICAL DICTIONARY. 



or five times around one of the wires, back of the joint, the wind- 
ing is then continued over the lapped portion, and a few more turns 
are taken around the other single wire. The whole is then soldered. 



Fig. 204. Britannia Joint. 

Joint, Butt. A joint in belting or in wire in which the ends to be 
joined are cut off square across, placed in contact and secured. It 
ensures even running when used in belting. Any irregularity in 
thickness of a belt affects the speed of the driven pulley. As 
dynamos are generally driven by belts, and it is important to drive 
them at an even speed to prevent variations in the electro-motive 
force, butt joints should be used on belting for them, unless a very 
perfect lap joint is made, which does not affect either the thickness 
or the stiffness of the belt. 

When a butt joint is used in wire a sleeve may be used to 
receive the abutting ends, which may be secured therein by 
soldering. This species of joint has been used on lightning rods 
and may more properly be termed a sleeve joint. 

Joint, Lap. (a) In belting a joint in which the ends are over- 
lapped, and riveted or otherwise secured in place. If made with- 
out reducing the thickness of the ends it is a bad joint for electrical 
work, as it prevents even running of machinery to which it is 
applied. Hence dynamo belts should be joined by butt joints, or 
if by lap joints the ends should be shaved off so that when joined 
and riveted, there will be no variation in the thickness of the belt. 

(b) In wire lap joints are made by overlapping the ends of the 
wire and soldering or otherwise securing. The Britannia joint 
(see Joint, Britannia,) may be considered a lap-joint. 

Joint, Marriage. A joint for stranded conductors used for 
Galende's cables. It is made somewhat like a sailor's long splice. 
Bach one of the strands is wound separately into the place whence 
the opposite strand is unwound and the ends are cut off so as to 
abutt. In this way all are smoothly laid in place and soldering is 
next applied. 





Fig. 205 . Marriage Joint. 

Joint, Sleeve. A joint in electric conductors, in which the ends 
of the wires are inserted into and secured in a metallic sleeve or 
tube, whose internal diameter is just sufficient to admit them. 



STANDARD ELECTRICAL DICTIONARY. 311 

Joint, Splayed. The method of joining the ends of stranded 
conductors. The insulating covering is removed, the wires are 
opened out, and the center wire, heart or core of the cable is cut 
off short. The two ends are brought together, the opened out 
wires are interlaced or crotched like the fingers of the two hands, 
and the ends are wound around the body of the cable in opposite 
directions. The joint is trimmed and well soldered. Tinned wire 
with rosin flux for the soldering is to be recommended. Insu- 
lating material is finally applied by hand, with heat if necessary. 

Joints in Belts. Belt-joints for electric plants where the belts 
drive dynamos should be made with special care. The least 
inequality affects the electro-motive force . Butt j oints are , generally 
speaking, the best, where the ends of the belt are placed in contact 
and laced. Lap-joints are made by overlapping the belt, and 
unless the belt is carefully tapered so as to preserve uniform 
strength, the speed of the dynamo will vary and also the electro- 
motive force. 

Jotllad. A name proposed to be substituted for "joule," q. v. 
It has not been adopted. 

Joule. This term has been applied to several units. 

(a) The practical C. G. S. unit of electric energy and work — the 
volt-coulomb. It is equal to io 7 ergs — 0.73734 foot pound — 
.00134 horse power seconds. A volt-ampere represents one joule 
per second. 

(6) It has also been used as the name of the gram-degree C. 
thermal unit — the small calorie. 

Synonym — Joulad. 

Joule Effect. The heating effect of a current passing through a 
conductor. It varies with the product of the resistance by the 
square of the current, or with C 2 R. 

Joule's Equivalent. The mechanical equivalent of heat, which 
if stated in foot-pounds per pound-degree F. units, is 772 (772.55). 
(See Equivalents.) 

Junction Box. In underground distribution systems, an iron 
casing or box in which the feeders and mains are joined, and 
where other junctions are made. 

Synonym — Fishing Box. 

K. The symbol for electrostatic capacity. 

Kaolin. A product of decomposition of feldspar, consisting 
approximately of silica, 45, alumina, 40, water, 15. It was used in 



312 STANDARD ELECTRICAL DICTIONARY. 

electric candles of the Jablochkoff type as a constituent of the insu- 
lating layer or colombin. Later it was abandoned for another 
substance, as it was found that it melted and acted as a conductor. 

Kapp Line of Force. A line of force proposed by Kapp. It is 
equal to 6,000 C. G. S. lines of force, and the unit of area is the 
square inch. Unfortunately it has been adopted by many manu- 
facturers, but its use should be discouraged, as it is a departure 
from the uniform system of units. 

One Kapp line per square inch = 930 C. G. S. lines per square 
centimeter. 

Kathelectrotonus. A term used in medical electricity or elec- 
tro-therapeutics to indicate the increased functional activity induced 
in a nerve by the proximity of the kathode of an active circuit 
which is completed through the nerve. The converse of anelectro- 
tonus. 

Kathode. The terminal of an electric circuit whence an electro- 
lyzing current passes from a solution. It is the terminal connected 
to the zinc plate of a primary battery. 

Kathodic Closure Contraction. A term in electro- therapeutics ; 
the contractions near where the kathode of an active circuit is 
applied to the body, which are observed at the instant when the 
circuit is closed. 

Kathodic Duration Contraction. A term in electro-thera- 
peutics ; the contraction near where the kathode of an active circuit 
is applied to the body for a period of time. 

K. C. C. Abbreviation for Kathodic Closure Contraction, q. v. 

K. D. C. Abbreviation for Kathodic Duration Contraction, q. v. 

Keeper. A bar of soft iron used to connect the opposite poles 
of a horseshoe magnet or the opposite poles of two bar magnets 
placed side by side. It is designed to prevent loss of magnetism. 
The armature of a horseshoe magnet is generally used as its 
keeper. For bar magnets a keeper is used for each end, the mag- 
nets being laid side by side, with their poles in opposite direction 
but not touching, and a keeper laid across at each end connecting 
the opposite poles. 

Kerr Effect. The effect of an electrostatic field upon polarized 
light traversing a dielectric contained within the field. (See Elec- 
trostatic Refraction . ) 

Kerr's Experiment. Polarized light reflected from the polished 
face of a magnet pole has its plane of polarization rotated ; when it 
is reflected from the north pole the rotation is from left to right. 



STANDARD ELECTRICAL DICTIONARY. 



3*3 



Key. A switch adapted for making and breaking contact easily 
when worked by hand, as a Morse telegraph key. 



Key Board. 

mounted. 



A board or tablet on which keys or switches are 



Key=board. (a) A switch board, q. v. 

(b) A set of lettered keys similar to those of a typewriter 
employed in some telegraph instruments. As each key is depressed 
it produces the contact or break requisite for the sending of the 
signal corresponding to the letter marked upon the key. The 
signal in printing telegraphs, on which such key-boards are used, 
is the reprinting of the letter at the distant end of the line. 

Key, Bridge. A key for use with a Wheats tone Bridge, q.v. It 
it desirable to first send a current through the four arms of the 
bridge in using it for testing resistances and then through the 
galvanometer, because it takes a definite time for the current to 
reach its full strength. This is especially the case if the element 
being measured has high static capacity, as a long ocean cable. If 
the galvanometer connections were completed simultaneously with 
the bridge connections a momentary swing would be produced 
even if the arms bore the proper relation to each other. This 
would cause delay in the testing* A bridge key avoids this by first 
connecting the battery circuit through the arms of the bridge, and 
then as it is still further depressed the galvanometer circuit is 
completed. 




Fig - . 206. Charge and Discharge Key 

Key, Charge and Discharge. A key for use in observing the 
discharge of a condenser immediately after removing the battery. 



3U 



STANDARD EIvECTRICAIy DICTIONARY. 



In one typical form it has two contacts, one below and one above, 
and being a spring in itself is pressed up against the upper one. 
Connections are so made that when in its upper position it brings 
the two coatings of the condenser in circuit with the galvanom- 
eter. When depressed it does the same for a battery. In use it 
is depressed and suddenly released when the galvanometer receives 
the full charge, before there has been time for leakage. This is 
one method of connection illustrating its principle. 

In the cut L is the spring-key proper. S 2 is the upper contact 
screw against which the spring normally presses. In this position 
the galvanometer G is in circuit with the opposite coatings of the 
condenser C. On depressing the contact S 2 is broken and S 1 is 
made. This brings the battery B in circuit with the condenser 
coatings. On releasing the key it springs up and the galvanometer 
receives the effect of the charge of the condenser as derived from 
the battery. 

Key, Double Contact. A key arranged to close two distinct 
circuits, holding the first closed until the second is completed. It 
is used for Wheatstone bridge work. 

C 




Fig. 207. Kempe's Discharge Key. 

Key, Double Tapper. A telegraph key giving contacts alter- 
nately for currents in opposite directions, used in needle telegraphy. 

Key, Increment. A key for use in duplex and quadruplex 
telegraphy. Its action is to increase the line current, not merely to 
suddenly turn current into it. 



STANDARD ELECTRICAL DICTIONARY. 315 

Key, Kempe's Discharge. A key giving a charging, discharg- 
ing and insulating connection, for static condenser work. 
Referring to the cut / is a lever or spring with upper discharging 
contact s, and lower charging contact s / . In use it is pressed 
down by the insulating handle or linger piece C, until caught by 
the hook attached to the key /. This hook is lower down than that 
on the key D, and holds it in contact with the charging contact 
piece S'. On pressing the key /, marked or designated " Insulate," 
it springs up, breaks contact at S' ', and catching against the hook 
on D, which key is designated "Discharge," remains insulated 
from both contacts ; next on pressing D it is released and springs 
up and closes the discharge contact .S. It is a form of charge and 
discharge key. (See Key, Charge and Discharge.) 

Key, Magneto=electric. A telegraph key whose movements 
operate what is virtually a small magneto-generator, so as to pro- 
duce currents of alternating direction, one impulse for each motion 
of the key. It is employed for telegraphing without a line battery, 
a polarized relay being used. In one very simple form a key is 
mounted on a base with a permanent magnet and connected to the 
armature, so that when the key is pressed downwards it draws the 
armature away from the poles of the magnet. If the magnet or its 
armature is wound with insulated wire this action of the key will 
cause instantaneous currents to go through a circuit connected to 
the magnet 01 armature coils. 




Fig. 208. Siemens' Magneto-electric Key. 

In Siemens & Halske's key an H armature E is pivoted between 
the poles N S, of a powerful compound horseshoe magnet, G G. 
It is wound with fine wire and a key handle H is provided for 
working it. In its normal position the handle is drawn upward, 
and the end s s of the armature core is in contact with the south 
pole .S of the permanent magnet, and the end n 71 with the north 
pole. This establishes the polarity of the armature. On depress- 
ing the key the contacts are broken and in their place the end 
n n comes in contact with the south pole and the end s s with 




316 STANDARD ELECTRICAL DICTIONARY. 

the north pole. This suddenly reverses the polarity of the arma- 
ture and sends a momentary current through the armature coil 
which is in circuit with the line. The cut only shows the principle 
of the key, whose construction is quite complicated. 

Key, Make and Break. An ordinary electric key, usually mak- 
ing a contact when depressed, and rising by 
spring action when released, and in its rise break- 
ing the contact. 

Key, Plug. An appliance for closing a circuit. 
Two brass blocks are connected to the terminals, 
but are disconnected from each other. A brass 
plug slightly coned or with its end split so as to 
Plug Key. give it spring action is thrust between the blocks 
to complete the circuit. It is used in Resist- 
ance coils and elsewhere. (See Coil, Resistance.) Grooves are 
formed in the blocks to receive the plug. 

Key, Reversing, (a) A double key, arranged so that by depress- 
ing one key a current flows in one direction, and by depressing the 
other a current flows in the opposite direction. It is used in con- 
nection with a galvanometer in experimental, testing or measuring 
operations. 

(b) A key effecting the same result used in quadruplex telegraphy. 

Key, Sliding=Contact. A name given to the key used for 
making instantaneous contacts with the metre wire of a metre 
bridge, q. v. The name is not strictly correct, because it is impor- 
tant that there should be no sliding contact made, as it would wear 
out the wire and make it of uneven resistance. 

It is a key which slides along over the wire and which, when 
depressed, presses a platinum tipped knife edge upon the wire. 
On being released from pressure the key handle springs up and 
takes the knife edge off the wire. This removal is essential to avoid 
wearing the wire, whose resistance per unit of length must be 
absolutely uniform. 

Key, Telegraph. The key used in telegraphy for sending cur- 
rents as desired over the line. It consists of a pivoted lever with 
finger piece, which lever when depressed makes contact between 
a contact point on its end and a stationary contact point on the 
base. This closes the circuit through the line. When released it 
springs up and opens the line circuit. 

Kilo. A prefix to the names of units ; it indicates one thousand 
times, as kilogram, one thousand grams. A few such units are 
given below. 

Kilodyne. A compound unit ; one thousand dynes. (See Dyne.) 



STANDARD ELECTRICAL DICTIONARY, 317 

Kilogram. A compound unit; one thousand grams; 2.2046 
pounds avds. 

Kilo joule. A compound unit ; one thousand jo ules, q. v. 

Kilometer. A compound unit ; one thousand meters ; 3280.899 
feet ; 0.621382 statute miles. (See Meter.) 

Kilowatt. A compound unit ; one thousand watts, q. v. 

Kine. An absolute or C. G. S. unit of velocity or rate of motion; 
one centimeter per second ; proposed by the British Association. 

Kirchoff's Laws. These relate to divided circuits. I. When 
a steady current branches, the quantity of electricity arriving by the 
single wire is equal to the quantity leaving the junction by the 
branches. The algebraical sum of the intensities of the currents 
passing towards (or passing from) the junction is equal to zero ; 
^ C =0 (Daniell.) In the last sentence currents flowing towards 
the point are considered of one sign and those flowing away from 
it of the other. 

II. In a metallic circuit comprising within it a source of perma- 
nent difference of potential, E, the products of the intensity 
of the current within each part of the circuit into the corre- 
sponding resistance are, if the elements of current be all taken 
in cyclical order together, equal to E ; 2 (C r) =E. In a metallic 
circuit in which there is no source of permanent difference of 
potential E = o, and 2 (C r) = o. 

This law applies to each several mesh of a wire network as well 
as to a single metallic loop, and it holds good even when an 
extraneous current is passed through the loop. (Daniell.) 

In this statement of the two laws E stands for electro-motive 
force ; C for current intensity ; and r for resistance of a single 
member of the circuit. 

Knife=edge Suspension. The suspension of an object on a 
sharp edge of steel or agate. The knife edge should abut against 
a plane. The knife edge is generally carried by the poised object. 
Its edge then faces downward and on the support one or more 
plane or approximately plane surfaces are provided on which it 
rests. In the ordinary balance this suspension can be seen. It is 
sometimes used in the dipping needle. 

It is applied in cases where vertical oscillations are to be pro- 
vided for. 

Knot. The geographical mile ; a term derived from the knots 
on the log line, used by navigators. It is equal to 6,087 f ee t- 
Synonyms — Nautical Mile — Geographical Mile. 
Kohlrausch's Law. A law of the rate of travel of the elements 



318 STANDARD ELECTRICAL DICTIONARY. 

and radicals in solutions under the effects of electrolysis. It states 
that each element under the effects of electrolysis has a rate of 
travel for a given liquid, which is independent of the element with 
which it was combined. The rates of travel are stated for different 
elements in centimeters per hour for a potential difference of one 
or more volts per centimeter of path. 

Kookogey's Solution. An acid exciting and depolarizing 
solution for a zinc-carbon couple, such as a Bunsen battery. Its 
formula is : Potassium bichromate, 227 parts ; water, boiling, 
1,134 parts ; while boiling add very carefully and slowly 1,558 
parts concentrated sulphuric acid. All parts are by weight. Use 
cold. 

Krizik's Cores. Cores of iron for use with magnetizing coils, 
q. v. They are so shaped, the metal increasing in quantity per 
unit of length, as the centre is approached, that the pull of the 
excited coil upon them will as far as possible be equal in all 
positions. A uniform cylinder is attracted with varying force 
according to its position ; the Krizik bars or cores are attracted 
approximately uniformly through a considerable range. 

L. Symbol for length and also for the unit of inductance or 
coefficient of induction, because the dimensions of inductance are 
length. 

Lag, Angle of. (a) The angle of displacement of the magnetic axis 
of an armature of a dynamo, due to its magnetic lag. The axis of 
magnetism is displaced in the direction of rotation. (See Magnetic 
Lag.) 

(b) The angle expressing the lag of alternating current and 
electro-motive force phases. 

Laminated, adj. Made up of thin plates, as a laminated arma- 
ture core or converter core. 

Lamination. The building up of an armature core or other thing 
out of plates. The cores of dynamo armatures or of alternating 
current converters are often laminated. Thus a drum armature 
core may consist of a quantity of thin iron discs, strung upon a rod 
and rigidly secured, either with or without paper insulation between 
the discs. If no paper is used the film of oxide on the iron is relied 
on for insulation. The object of lamination is to break up the 
electrical continuity of the core, so as to avoid Foucault currents. 
(See Currents, Foucault.) The laminations should be at right 
angles to the direction of the Foucault currents which would be 
produced, or in most cases should be at right angles to the active 
parts of the wire windings. 



STANDARD ELECTRICAL DICTIONARY. 



319 



Lamination of Armature Conductors. These are sometimes 
laminated to prevent the formation of eddy currents. The lamina- 
tion should be radial, and the strips composing it should be insu- 
lated from each other by superficial oxidation, oiling or enamelling, 
and should be united only at their ends. 



s 



Fig-. 210. Pilsen Arc Lamp. 
Lamp, Arc. A lamp in which the light is produced by a vol- 
taic arc. Carbon electrodes are almost universally employed. 
Special mechanism, operating partly by spring or gravity and partly 
by electricity, is employed to regulate the distance apart of the 



320 



STANDARD KLKCTRICAL DICTIONARY. 



carbons, to let them touch when no current passes, and to separate 
them when current is first turned on. 

The most varied constructions have been employed, examples of 
which will be found in their places. Lamps may in general be 
divided into classes as follows, according to their regulating mech- 
anism and other features : 

(a) Single light regulators or monophotes. Ivamps through 
whose regulating mechanism the whole current passes. These are 
only adapted to work singly ; if several are placed in series on the 
same circuit, the action of one regulator interferes with that of the 
next one. 

(b) Multiple light regulators or polyphotes. In these the regu- 
lating mechanism and the carbons with their arc are in parallel ; 

the regulating device may be a single magnet or 
solenoid constituting a derived or shunt-circuit 
lamp, or it may include two magnets working 
differentially against or in opposition to each 
other constituting a differential lamp. 

(c) Lamps with fixed parallel carbons termed 
candles (q. v., of various types). 

(d) Lamps without regulating mechanism. 
These include lamps with converging carbons, 
whose object was to dispense with the regulating 
mechanism, but which in some cases have about 
as much regulating mechanism as any of the 
ordinary arc lamps. 

Lamp, Contact. A lamp depending for its 
action on loose contact between two carbon elec- 
trodes. At the contact a species of incandescence 
I with incipient arcs is produced. One of the 

electrodes is usually flat or nearly so, and the 
other one of pencil shape rests upon it. 
Lamp, Differential Arc. An arc lamp, the 
_ k regulation of the distance between whose carbons 

depends on the differential action of two separate 
electrical coils. The diagram illustrates the prin- 
ciple. The two carbons are seen in black ; the 
upper one is movable, The current arrives at A. 
It divides, and the greater part goes through the 
Fig. 211. Diagram low resistance coil M to a contact roller r> and 
of the Pilsen thence D y the frame to the upper carbon, and 
Lamp. RENTIAL RC through the arc and lower carbon to B, where 
it leaves the lamp. A smaller portion of the 
current goes through the coil M 1 of higher resistance and leaves 





STANDARD ELECTRICAL DICTIONARY. 



321 



the lamp also at B. A double conical iron core is seen, to which 
the upper carbon holder is attached. This is attracted in opposite 
directions by the two coils. If the arc grows too long its resistance 
increases and the coil M x receiving more current draws it down and 
thus shortens the arc. If the arc grows too short, its resistance 
falls, and the coil M receives more current and drawls the core up- 
wards, thus lengthening the arc. This differential action of the two 
cores gives the lamp its name. R is a pulley over wmich a cord 
passes, one end attached to the core and the other to a counterpoise 
weight, W. 

Lamp, Holophote. A lamp designed for use alone upon its own 
circuit. These have the regulating mechanism in series with the 
carbon and arc, so that the whole current goes 
through both. (See Lamp, Arc.) 

Synonym — Monophote Lamp. 

Lamp=hour. A unit of commercial supply 
of electric energy ; the volt-coulombs re- 
quired to maintain an electric lamp for one 
hour. A sixteen-candle power incandescent 
lamp is practically the lamp alluded to, and 
requires about half an ampere current at 110 
volts, making a lamp-hour equal to about 
198,000 volt-coulombs. 

Lamp, Incandescent. An electric lamp 
in which the light is produced by heating 
to whiteness a refractory conductor by the 
passage of a current of electricity. It is dis- 
tinguished from an arc lamp (which etymo- 
logically is also an incandescent lamp) by the 
absence of any break in the continuity of its 
refractory conductor. Many different forms 
and methods of construction have been tried, 
but now all have settled into approximately 
the same type. 



The incandescent lamp consists of a small 
glass bulb, called the lamp-chamber, which is 
exhausted of air and hermetically sealed. It 
contains a filament of carbon, bent into a 
loop of more or less simple shape. This shape 
prevents any tensile strain upon the loop and 
also approximates to the outline of a regular flame. 

The loop is attached at its ends to two short pieces of platinum 
w 7 ire, wmich pass through the glass of the bulb and around which 
the glass is fused. As platinum has almost exactly the same 




Fig. 212. Incandescent 
Electric Lamp. 



322 STANDARD ELECTRICAL DICTIONARY. 

coefficient of heat-expansion as glass, the wires do not canse the 
glass to crack. 

The process of manufacture includes the preparation of the fila- 
ment. This is made from paper, silk, bamboo fibre, tamidine, q. 
v. , or other material. After shaping into the form of the filament 
the material is carbonized at a high heat, while embedded in char- 
coal, or otherwise protected from the air. The flashing process 
(see Flashing of Incandescent Lamp Carbons) may also be applied. 
The attachment to the platinum wires is effected by a minute clamp 
or by electric soldering. The loop is inserted and secured within 
the open globe, which the glass blower nearly closes, leaving one 
opening for exhaustion. 

The air is pumped out, perhaps first by a piston pump, but 
always at the end by a mercurial air pump. (See Pump, Geissler — 
and others.) As the exhaustion becomes high a current is passed 
through the carbons heating them eventually to white heat so as to 
expel occluded gas. The occluded gases are exhausted by the 
pump and the lamp is sealed by melting the glass with a blowpipe 
or blast-lamp flame. For the exhaustion several lamps are usually 
fastened together by branching glass tubes, and are sealed off one 
by one. 

The incandescent lamps require about 3^ watts to the candle 
power, or give about 12 sixteen-candle lamps to the horse power 
expended on them. 

Generally incandescent lamps are run in parallel or on multiple 
arc circuits. All that is necessary in such distribution systems is 
to maintain a proper potential difference between the two leads 
across which the lamps are connected. In the manufacture of lamps 
they are brought to an even resistance and the proper voltage at 
which they should be run is often marked upon them. This may 
be fifty volts and upward. One hundred and ten volts is a very 
usual figure. As current one ampere for a fifty-volt, or about one- 
half an ampere for a one hundred and ten volt lamp is employed. 

Lamp, Incandescent, Three Filament. A three filament lamp 
is used for three phase currents. It has three filaments whose 
inner ends are connected, and each of which has one leading-in 
wire. The three wires are connected to the three wires of the circuit. 
Each filament receives a current varying in intensity, so that 
there is always one filament passing a current equal to the sum of 
the currents in the other two filaments. 

Lamp, Lighthouse. A special type of arc light. It is adapted 
for use in a lighthouse dioptric lantern, and hence its arc has 
to be maintained in the same position, in the focus of the lenses. 
The lamps are so .constructed as to feed both carbons instead of 
only one, thereby securing the above object. 



STANDARD ELECTRICAL DICTIONARY. 323 

Lamp, Pilot. A lamp connected to a dynamo, and used by its 
degree of illumination to show when the dynamo on starting 
becomes excited, or builds itself up. 

Lamp, Polyphote. An arc lamp adapted to be used, a number 
in series, upon the same circuit. The electric regulating mechan- 
ism is placed in shunt or in parallel with the carbons and arc. (See 
Lamp, Arc.) 

Lamps, Bank of. A number of lamps mounted on a board or 
other base, and connected to serve as voltage indicator or to show 
the existence of grounds, or for other purposes. 

Lamp, Semi=incandescent. A lamp partaking of the character- 
istics of both arc and incandescence ; a lamp in which the imperfect 
contact of two carbon electrodes produces a part of or all of the 
resistance to the current which causes incandescence. 

The usual type of these lamps includes a thin carbon rod which 
rests against a block of carbon. The species of arc formed at the 
junction of the two heats the carbons. Sometimes the upper car- 
bon or at least its end is heated also by true incandescence, the 
current being conveyed near to its end before entering it. 

Semi-incandescent lamps are not used to any extent now. 

Lamp Socket. A receptacle for an incandescent lamp ; the 
lamp being inserted the necessary connections with the two leads 
are automatically made in most sockets. The lamps may be screwed 
or simply thrust into the socket and different ones are constructed 
for different types of lamps. A key for turning the current on and 
off is often a part of the socket. 

Latent Electricity. The bound charge of static electricity. 

(See Charge, Bound.) 

Law of Intermediate Metals. A law of thermo-electricity. The 
electro-motive force between any two metals is equal to the sum of 
electro-motive forces between each of the two metals and any inter- 
mediate metal in the thermo-electric series, or the electro-motive 
force between any two metals is equal to the sum of the electro- 
motive forces between all the intermediate ones and the original 
two metals ; it is the analogue of Volta's Law, q. v. 

Law of Inverse Squares. When force is exercised through 
space from a point, its intensity varies inversely with the square of 
the distance. Thus the intensity of light radiated by a luminous 
point at twice a given distance therefrom is of one-fourth the inten- 
sity it had at the distance in question. Gravitation, electric and 
magnetic attraction and repulsion and other radiant forces are 
subject to the same law. 



324 STANDARD ELECTRICAL DICTIONARY. 

Law of Successive Temperatures. A law of thermo-elec- 
tricity. The electro-motive force due to a given difference of 
temperature between the opposite junctions of the metals is equal 
to the sum of the electro-motive forces produced by fractional 
differences of temperature, whose sum is equal to the given differ- 
ence and whose sum exactly fills the given range of temperature. 

Law, Right=handed Screw. This rather crude name is given 
by Emtage to a law expressing the relation of direction of current 
in a circuit to the positive direction of the axis of a magnet acted 
on by such current. It is thus expressed : A right-handed screw 
placed along the axis of the magnet and turned in the direction of 
the current will move in the positive direction, i. e. y towards the 
north pole of the axis of the magnet. 

Lead. A metal ; one of the elements ; symbol Pb. Atomic 
weight, 207 ; equivalent, 103^ ; valency, 2. Lead may also be a 
tetrad, when its equivalent is 51.75. The following data are at o° C. 
(32 ° F.) with compressed metal : 

Relative Resistance, ( Silvers 1) 13-05 

Specific Resistance, !9«63 microhms. 

Resistance of a wire, 

(a) 1 ft. long, weighing 1 grain, 3.200 ohms. 

(b) 1 meter long, weighing 1 gram, 2.232 " 

(c) 1 meter long, 1 millimeter thick, .2498 " 
Resistance of 1 inch cube, 7.728 microhms. 
Electro-Chemical Equivalent (Hydrogen=.oio5) 1.086 mgs. 

Leading Horns. The tips of pole pieces in a dynamo, which 
extend in the direction of movement of the armature. 

Leading=in Wires. The platinum wires passing through the 
glass of an incandescent lamp-chamber, to effect the connection of 
the carbon filament with the wires of the circuit. 

Lead of Brushes, Negative. In a motor the brushes are set 
backwards from their normal position, or in a position towards the 
direction of armature rotation or given a negative lead instead of 
a positive one, such as is given to dynamo brushes. 

Leak. A loss or escape of electricity by accidental connection 
either with the ground or with some conductor. There are various 
kinds of leak to which descriptive terms are applied. 

Leakage. The loss of current from conductors ; due to ground- 
ing at least at two places, or to very slight grounding at a great 
many places, or all along a line owing to poor insulation. In aerial or 
pole telegraph lines in wet weather there is often a very large leak- 
age down the wet poles from the wire. (See Surface Leakage — 
Magnetic Leakage!) 



STANDARD ELECTRICAL DICTIONARY. 325 

Leakage Conductor. A conductor placed on telegraph poles to 
conduct directly to earth any leakage from, a wire and thus prevent 
any but a very small portion finding its way into the other wires 
on' the same pole. It presents a choice of evils, as it increases the 
electrostatic capacity of the line, and thus does harm as well as good. 
It consists simply of a wire grounded and secured to the pole. 

Leg of Circuit. One lead or side of a complete metallic circuit. 

Lenz's Law. A law expressing the relations of direction of an 
inducing current or field of force to the current induced by any 
disturbance in the relations between such field and any closed' con- 
ductor within its influence. It may be variously expressed. 

(a) If the relative position of two conductors, A andB, be changed, 
of which A is traversed by a current, a current is induced in B in 
such a direction that, by its electro-dynamic action on the current 
in A, it would have imparted to the conductors a motion of the 
contrarv kind to that bv which the inducing action was produced. 
(Ganot.) 

(5) The new (induced) current will increase the already existing 
resistances, or develop new resistance to that disturbance of the 
field which is the cause of induction. iDaniell.) 

(c) When a conductor is moving in a magnetic field a current 
is induced in the conductor in such a direction as by its mechanical 
action to oppose the motion. (Emtage.) 

(d) The induced currents are such as to develop resistance to the 
change brought about. 

Letter Boxes, Electric. Letter boxes with electrical con- 
nections to a bell or indicator of some sort, which is caused to act 
by putting a letter into the box. 

Leyden Jar. A form of static condenser. 

In its usual form it consists of a glass jar. Tinfoil is pasted around 
the lower portions of its exterior and interior surfaces, covering 
from one-quarter to three-quarters of the walls in ordinary examples. 
The rest of the glass is preferably shellacked or painted over with 
insulating varnish, q. v. The mouth is closed with a wooden or 
cork stopper and through its centre a brass rod passes which by a 
short chain or wire is in connection with the interior coating of the 
jar. The top of the rod carries a brass knob or ball. 

If such a jar is held by the tinfoil-covered surface in one hand and 
its knob is held against the excited prime conductor of a static 
machine its interior becomes charged ; an equivalent quantity of 
the same electricity is repelled through the person of the experi- 
menter to the earth and when removed from the conductor it will 
be found to hold a bound charge. If the outer coating and knob 



326 



STANDARD ELECTRICAL DICTIONARY. 



are both touched or nearly touched by a conductor a disruptive 
discharge through it takes place. 

If one or more persons act as discharging conductors they will 




Fig. 213. Leyden Jar with Discharger. 

receive a shock. This is done by their joining hands, a person at 
one end touching the outer coating and another person at the other 
end touching the knob. 

From an influence machine a charge can be taken by connecting 
the coating to one electrode and the knob to the other. 





Fig. 214. Sulphuric Acid Leyden Jar. 

Leyden Jar, Sir William Thomson's. An especially efficient 
form of Leyden jar. It consists of ajar with outer tinfoil coating 



STANDARD ELECTRICAL DICTIONARY. 327 

only. For the interior coating is substituted a quantity of concen- 
trated sulphuric acid. The central rod is of lead with a foot, which 
is immersed in the acid and from which the rod rises. A wooden 
cover partly closes the jar, as the central tube through which the 
rod passes is so large as not to allow the wood to touch it. Thus 
any leakage from inner to outer coating has to pass over the inside 
and outside glass surfaces. In the common form of jar the 
wooden cover may short circuit the uncoated portion of the 
inner glass surface. In the cut a simplified form of Thomson's 
Leyden jar is shown, adapted for scientific work. 

Lichtenberg's Figures. If the knob of a Leyden jar or other 
exited electrode is rubbed over the surface of ebonite, shellac, resin 
or other non-conducting surface it leaves it electrified in the path 
of the knob. If fine powder such as flowers of sulphur or lycopo- 
dium is dusted over the surface and the excess is blown away, the 
powder will adhere where the surface was electrified, forming what 
are called Lichtenberg's Figures, Lycopodium and sulphur show 
both positive and negative figures, that is to say, figures produced 
by a positively or negatively charged conductor. Red lead adheres 
only to negative figures. If both positive and negative figures are 
made and the surface is sprinkled with both red lead and flowers 
of sulphur each picks out its own figure, the sulphur going princi- 
pally to the positive one. 

The red lead takes the form of small circular heaps, the sulphur 
arranges itself in tufts with numerous diverging branches. This in- 
dicates the difference in the two electricities. The figures have been 
described as "a very sensitive electrosope for investigating the 
distribution of electricity on an insulating surface." (Ganot.) 

Life of Incandescent Lamps. The period of time a lamp 
remains in action before the carbon filament is destroyed. The 
cause of a lamp failing may be the volatilization of the carbon of 
the filament, causing it to become thin and to break ; or the 
chamber may leak. The life of the lamp varies ; 600 hours is a 
fair estimate. Sometimes they last several times this period. 

The higher the intensity at which they are used the shorter is 
their life. From their prime cost and the cost of current the most 
economical way to run them can be approximately calculated. 

Lightning. The electrostatic discharge to the earth or among 
themselves of clouds floating in the atmosphere. The discharge is 
accompanied by a spark or other luminous effect, which may be 
very bright and the effects, thermal and mechanical, are often of 
enormous intensity. 

The lightning flash is white near the earth, but in the upper 
regions where the air is rarefied it is of a blue tint, like the spark 
of the electric machine. The flashes are often over a mile in 



328 STANDARD ELECTRICAL DICTIONARY. 

length, and sometimes are four or five miles long. They have 
sometimes a curious sinuous and often a branching shape, which 
has been determined by photography only recently. To the eye 
the shape seems zigzag. 

In the case of a mile-long flash it has been estimated that 
3,516,480 De la Rue cells, q. v., would be required for the develop- 
ment of the potential, giving the flash over three and one-half 
millions of volts. But as it is uncertain how far the discharge is 
helped on its course by the rain drops this estimate may be too 
high. 

There are two general types of flash. The so-called zigzag flash 
resembles the spark of an electric machine, and is undoubtedly due 
to the disruptive discharge from cloud to earth. Sheet lightning 
has no shape, simply is a sudden glow, and from examination of 
the spectrum appears to be brush discharges (see Discharge, Brush) 
between clouds. Heat lightning is attributed to flashes below the 
horizon whose light only is seen by us. Globe or ball lightning 
takes the form of globes of fire, sometimes visible for ten seconds, 
descending from the clouds. On reaching the earth they sometimes 
rebound, and sometimes explode with a loud detonation. No 
adequate explanation has been found for them. 

The flash does not exceed one-millionth of a second in duration ; 
its absolute light is believed to be comparable to that of the sun, 
but its brief duration makes its total light far less than that of the 
sun for any period of time. 

If the disruptive discharge passes through a living animal it is 
often fatal. As it reaches the earth it often has power enough to 
fuse sand, producing fulgurites, q. v. (See also Back Shock or 
Stroke of Lightning,) 

Volcanic lightning, which accompanies the eruptions of volcanoes, 
is attributed to friction of the volcanic dust and to vapor con- 
densation. 

Lightning Arrester. An apparatus for use with electric lines 
to carry off to earth any lightning discharge such lines may pick up. 
Such discharge would imperil life as well as property in telegraph 
offices and the like. 

Arresters are generally constructed on the following lines. The 
line wires have connected to them a plate with teeth ; a second 
similar plate is placed near this with its teeth opposite to those of 
the first plate and nearly touching it. The second plate is con- 
nected by a low resistance conductor to ground. Any lightning 
discharge is apt to jump across the interval, of a small fraction of 
an inch, between the oppositely placed points and go to earth. 

Another type consists of two plates, placed face to face, and 
pressing between them a piece of paper or mica. The lightning is 



STANDARD ELECTRICAL DICTIONARY. 



329 



supposed to perforate this and go to earth. One plate is connected 
to the line, the other one is grounded. 




Fig. 215. Comb or Toothed Lightning Arrester. 

The lightning arrester is placed near the end of the line before it 
reaches any instrument. (See Alternative Paths.) 




Fig-. 216. Film or Plate Lightning Arrester. 

Lightning Arrester, Counter=electro=motive Force. An 

invention of Prof. Elihu Thompson. A lightning arrester in which 
the lightning discharge sets up a counter-electro-motive force 
opposed to its own. This it does by an induction coil. If a dis- 
charge to earth takes place it selects the primary of the coil as it 
has low self-induction. In its discharge it induces in the secondary 
a reverse electro-motive force which protects the line. 

Lightning Arrester Plates. The toothed plates nearly in con- 
tact, tooth for tooth, or the flat plates of a film lightning arrester, 
which constitute a lightning arrester. Some advocate restricting 
the term to the plate connected to the line. 

Lightning Arrester, Vacuum. A glass tube, almost com- 
pletely exhausted, into which the line wire is fused, while a wire 
leading to an earth connection has its end fused in also. 

A high tension discharge, such as that of lightning, goes to earth 
across the partial vacuum in preference to going through the line, 



33Q STANDARD ELECTRICAL DICTIONARY. 

which by its capacity and self-induction opposes the passage 
through it of a lightning discharge. 

It is especially adapted for underground and submarine lines. 

Lightning, Ascending. Lightning is sometimes observed which 
seems to ascend! It is thought that this may be due to positive 
electrification of the earth and negative electrification of the clouds. 

Lightning, Globe or Globular. A very unusual form of light- 
ning discharge, in which the flashes appear as globes or balls of 
light. They are sometimes visible for ten seconds, moving so 
slowly that the eye can follow them. They often rebound on 
striking the ground, and sometimes explode with a noise like a 
cannon. They have never been satisfactorily explained. Some- 
times the phenomenon is probably subjective and due to persistence 
of vision. 

Lightning Jar. A Leyden jar whose coatings are of metallic 
filings dusted on to the surface while shellacked, and before the 
varnish has had time to dry. In its discharge a scintillation of 
sparks appears all over the surface. 

Line of Contact. The line joining the points of contact of the 
commutator brushes in a dynamo or motor. 
Synonym — Diameter of Commutation. 

Lines of Force. Imaginary lines denoting the direction of 
repulsion or attraction in a, field of force, q. v. They may also be so 
distributed as to indicate the relative intensity of all different parts 
of the field. They are normal to equipotential surfaces. (See 
Electro-magnetic Lines of Force — Electrostatic Lines of Force — 
Magnetic Lines of Force. 

Lines of Induction. Imaginary lines within a body marking 
the direction taken within it by magnetic induction. These are 
not necessarily parallel to lines of force, but may, in bodies of uni- 
form agglomeration, or in crystalline bodies, take various directions. 

Synonym — Lines of Magnetic Induction. 

Lines of Slope. Lines in a field of force which mark the direc- 
tions in which the intensity of force in the field most rapidly falls 
away. 

Links, Fuse. Links made of more or less easily fusible metal, 
for use as safety fuses. 

Listening Cam. In a telephone exchange a cam or species of 
switch used to connect the operator's telephone with a subscriber's 
line. 



STANDARD ELECTRICAL DICTIONARY. 331 

Lithanode. A block of compressed lead binoxide, with platinum 
connecting foils for use as an electrode in a storage batter}-. It has 
considerable capacity, over 5 ampere-hours per pound of plates, but 
has not met with any extended adoption. 

Load, In a dynamo the amperes of current delivered by it 
under any given conditions. 

Local Action, (a) In its most usual sense the electric cur- 
rents within a battery, due to impurities in the zinc, which currents 
may circulate in exceedingly minute circuits, and which w T aste 
zinc and chemicals and contribute nothing to the regular current 
of the battery. Amalgamated or chemically pure zinc develops no 
local action. 

(b) The term is sometimes applied to currents set up within the 
armature core or pole pieces of a dynamo. (See Currents , Foucault. ) 

Local Battery. A battery supplying a local circuit (q. v.) ; in 
telegraphy, where it is principally used, the battery is thrown in 
and out of action by a relay, and its current does the work of actu- 
ating the sounder and any other local or station instruments. (See 
Relay.) 

Local Circuit. A short circuit on which are placed local appar- 
atus or instruments. Such circuit is of low resistance and its cur- 
rent is supplied by a local battery, q. v. Its action is determined 
by the current from the main line throwing its battery in and out 
of circuit by a relay, q. v., or some equivalent. 

Local Currents. Currents within the metal parts of a dynamo. 
(See Currents, Foucault.) In a galvanic battery where there is 
local action, q. v., there are also local currents, though they are not 
often referred to. 

Localization. Determining the position of anything, such as a 
break in a cable, or a grounding in a telegraph line. In ocean 
cables two typical cases are the localization of a break in the con- 
ductor and of a defect in the insulation admitting water. The 
first is done by determining the static capacity of the portion of 
the line which includes the unbroken portion of the conductor ; 
the other by determining the resistance of the line on a grounded 
circuit. 

Locus. A place. The word is used to designate the locality or 
position of, or series of positions of definite conditions and the 
like. Thus an isogonic line is the locus of equal declinations of 
the magnetic needle ; it is a line passing through all places on the 
earth's surface where the condition of a given declination is found 
to exist. 



332 STANDARD ELECTRICAL DICTIONARY. 

Lodestone. Magnetic magnetite ; magnetite is an ore of iron, 
Fe 3 4 , which is attracted by the magnet. Some samples possess 
poiarity and attract iron. The latter are lodestones. 

Synonym — Hercules Stone 

Logarithm. The exponent of the power to which it is necessary 
to raise a fixed number to produce a given number. The fixed 
number is the base of the system. 

There are two systems ; one, called the ordinary system, has 10 
for its base, the other, called the Naperian system, has 2.71828 for 
its base. The latter are also termed hyperbolic logarithms, and 
are only used in special calculations. 

Log, Electric. An apparatus for measuring the speed of a ship. 
A rotating helical vane of known pitch is dragged behind the 
vessel. As the helix rotates its movements may actuate electric 
machinery for registering its rotations. The number of these in a 
given time, multiplied by the pitch of the vane, gives the distance 
traversed in such time. 

Loop. A portion of a circuit introduced in series into another 
circuit. The latter circuit is opened by a spring-jack, q. v. or other 
device, and the loop inserted. By loops any number of connec- 
tions can be inserted into a circuit in series therewith, and in series 
or in parallel with one another. 

Loop Break. A double bracket or similar arrangement for 
holding on insulators the ends of a conductor which is cut between 
them, and to which are connected the ends of a loop. The space 
between the insulators may be about a foot. 

Luces. This may be used as the plural of lux, q. v. It is the 
I,atin plural. 

Luminous Jar. A Leyden jar whose coatings are of lozenge- 
shaped pieces of tinfoil between which are very short intervals. 
When discharged, sparks appear all over the surface where the 
lozenges nearly join. 

Lux. A standard of illumination, q. v., as distinguished from 
illuminating power. 

It is the light given by one candle at a distance of 12.7 inches — 
by a carcel, q. v., at a distance of one meter — or by 10,000 candles 
at 105.8 feet. 

It was proposed by W. H. Preece. All the above valuations are 
identical. 

M. (a) Symbol of gaseous pressure equal to one-millionth of an 
atmosphere. 



STANDARD ELECTRICAL DICTIONARY. 333 

(d) The Greek 1/1, /.i, is used as the symbol of magnetic permea- 
bility. 

Machine, Cylinder Electric. A frictional electric machine 
whose rotating glass is in the shape of a cylinder instead of a disc 
as in the more recent machines. 

Machine, Frictional Electric. An apparatus for development 
of high tension electricity by contact action, brought about by 
friction. 




Fig. 217. Plate Frictional Electric Machine. 

It consists of a plate or cylinder of glass mounted on insulating 
standards and provided with a handle for turning it. One or more 
cushions of leather are held on an insulated support, so as to rub 
against the plate or cylinder as it is turned. A metal comb or 
combs are held on another insulating support so as to be nearly in 
contact with the surface of the glass plate at a point as far removed 
as possible from the rubbers. The combs are attached to a brass 
ball or round-ended cylinder, which is termed the prime conductor. 

In use either the prime conductor or cushions are connected by 
a chain or otherwise with the earth. Assume it to be the cushions. 
As the machine is worked by turning the plate, the glass and 



334 STANDARD ELECTRICAL DICTIONARY. 

cushion being in contact develop opposite electricities. The glass 
is charged with positive electricity, and as it turns carries it off and 
as it reaches the prime conductor by induction and conduction 
robs it of its negative electricity. Meanwhile the cushions nega- 
tively excited deliver their charge to the earth. The action thus 
goes on, the prime conductor being charged with positive electricity. 

If the prime conductor is connected to the earth and the cushions 
are left insulated, negative electricity can be collected from the 
cushions. 

In some machines both prime conductor and cushions are kept 
insulated and without ground contact. Electrodes connecting with 
each are brought with their ends close enough to maintain a 
sparking discharge. 

Machine Influence. A static electric machine working by 
induction to build up charges of opposite nature on two separate 
prime conductors. In general they are based on the principle of 
the electrophorous. Work is done by the operator turning the 
handle. This rotates a disc and draws excited parts of it away 
from their bound charges. This represents a resistance to mechan- 
ical motion. The work absorbed in overcoming this mechanical 
resistance appears as electric energy. There are various types of 
influence machines, the Holtz, Toeppler-Holtz and Wimshurst 
being the most used. The electrophorous, q. v., is a type of 
influence machine. 

Machine, Holtz Influence. A static electric machine. It 
includes two plates, one of which is rapidly rotated in front of the 
other. Two armatures of paper are secured to the back of the 
stationary plate at opposite ends of a diameter. To start it one of 
these is charged with electricity. This charge by induction acts 
through the two thicknesses of glass upon a metal bar carrying 
combs, which lies in front of the further side of the movable plate. 
The points opposite the armature repel electrified air, which strikes 
the movable disc and charges it. A second rod with comb at the 
opposite end of the same diameter acts in the reverse way. Thus 
opposite sections of the disc are oppositely charged and the combs 
with them. By induction these portions of the disc react upon 
the two armatures. The opposite electricities escape from the 
armatures by paper tongues which are attached thereto and press 
against the back of the movable plate. As the plate rotates the 
opposite electricities on its face neutralize the electricity repelled 
from the combs. The charges on the back strengthen the charges 
of the armatures and brass combs. Thus the machine builds up , 
and eventually a discharge of sparks takes place from the poles of 
the brass combs. 

Machine, Toeppler=Holtz. A modification of the Holtz 



STANDARD ELECTRICAL DICTIONARY. 335 

machine. The priming charge of the armatures is produced by 
friction of metallic brushes against metallic buttons on the face of 
the rotating plate. (See Machine, Holtz.) 

Machine, Wimshurst. A form of static influence machine. It 
consists of two plates of glass, on which radial sectors of tinfoil 
are pasted. Both plates are rotated in opposite directions. The 
sectors of the two plates react one upon the other, and electric 
charges of opposite sign accumulate on the opposite sides of the 
plates and are collected therefrom by collecting combs. 

Mack. A name, derived from Maxwell, and suggested for the 
unit of inductance. It is due to Oliver Heaviside, but has never 
been adopted. (See Henry.) 

Magne=Crystallic Action. The action of a supposed force of 
the same name, proposed by Faraday. It relates to the different 
action of a magnetic field upon crystalline bodies, according to the 
position of their axes of crystallization. A needle of tourmaline, 
normally paramagnetic, if poised with its axis horizontal, is dia- 
magnetic. Bismuth illustrates the same phenomenon. The sub- 
ject is obscure. Faraday thought that he saw in it the action of a 
specific force. 

Magnet. A body which tends when suspended by its centre of 
gravity to lay itself in a definite direction, and to place a definite 
line within it, its magnetic axis, q. v., in a definite direction, 
which, roughly speaking, lies north and south. The same bodies 
have the power of attracting iron (Daniell), also nickel and cobalt. 

Magnets are substances which possess the power of attracting 
iron. (Ganot.) 

Magnet, Anomalous. A magnet possessing more than the 
normal number (two) of poles. If two straight magnets are placed 
end to end with their south poles in juxtaposition the compound 
bar will seem to possess three poles, one at each end and one in the 
middle. The apparent pole in the middle is really made up of 
two consequent poles, q. v. It sometimes happens that when a 
single long thin bar is magnetized consequent poles are produced, 
although such magnet is in one piece. This may be accidental, as 
in such case it is quite hard to avoid anomalous poles, or, as in 
the field magnets of some forms of dynamos, anomalous poles may 
be purposely produced. 

Magnet, Artificial. A magnet formed artificially by any 
method of magnetization (see Magnetism) applicable to permanent 
magnets, electro-magnets and solenoids. It expresses the distinc- 
tion from the natural magnets or lodestone, q. v. It is made of 
steel in practice magnetized by some of the methods described 
under Magnetization, 



336 STANDARD ELECTRICAL DICTIONARY. 

Magnet, Axial. A straight solenoid with axial core. 

Magnet, Bar. A bar magnet is one in the shape of a bar, i. e., 
straight with parallel sides and considerably longer than wide or 
deep. 

Magnet, Bell = shaped. A form of permanent magnet used in 
some galvanometers. In shape it is a thick-sided cylindrical box 
with two slots cut out of opposite sides, so as to make it represent 
a horseshoe magnet. Its shape enables it to be surrounded 
closely by a mass of copper, for damping its motion, to render the 
instrument dead-beat. Such a magnet is used in Siemens & 
Halske's galvanometer. 

Magnet Coil. A coil to be thrust over an iron core, to make an 
electro-magnet. They are often wound upon paper or wooden 
bobbins or spools, so as to be removable from the core if desired. 

Magnet, Compensating, (a) A magnet fastened near a com- 
pass on an iron or steel ship to compensate the action of the metal 
of the ship upon the magnetic needle. The ship itself always has 
some polarity and this is neutralized by one or more compensating 
magnets. 

{b) See below. 

Magnet, Controlling. A magnet attached to a galvanometer by 
which the directive tendency of its magnetic needle is adjusted. 
In the reflecting galvanometer it often is a slightly curved magnet 
carried by a vertical brass spindle rising from the center of the 
instrument, and which magnet may be slid up and down on the 
spindle to regulate or adjust its action. 

Synonym — Compensating Magnet. 

Magnet, Compound. A permanent magnet, built up of a 
number of magnets. Small bars can be more strongly magnetized 
than large. Hence a compound magnet may be made more power- 
ful than a simple one. 

Magnet Core. The iron bar or other mass of iron around which 
insulated wire is wound for the production of an electro-magnet. 
The shapes vary greatly, especially for field magnets of dynamos 
and motors. For these they are usually made of cast iron, although 
wrought iron is preferable from the point of view of permeability. 

Magnet, Damping. A damping magnet is one used for bringing 
an oscillating body to rest. The body may be a metallic disc or 
needle, and the action of the magnet depends on its lines of force 
which it establishes, so that the body has to cut them, and hence has 
its motion resisted. 



STANDARD ELECTRICAL DICTIONARY. 



337 



Magnet, Deflection of. The change of position of a magnet 
from the plane of the earth's meridian in which it normally is at 
rest into another position at some angle thereto, by the effect of an 
artificial magnetic field, as the deflection of a galvanometer needle. 

Magnet, Electro=. A magnet consisting of a bar of iron, bundle 
of iron wires, iron tube or some equivalent, around which a coil 
of insulated wire' is wound. Such combination becomes polarized 
when a current is passed through it and is an active magnet. On 
the cessation of the current its magnetism in part or almost com- 
pletely disappears. (See Electro-magnet.) 

Magnet, Equator of. In a magnet the locus of points of no 
attractive power and of no polarity. In a symmetrical, evenly 
polarized magnet it is the imaginary line girdling the centre. The 
terms Neutral Point or Neutral Line have displaced it. 

Synonyms — Neutral Line — Neutral Point. 

Magnet, Field. A magnet, generally an electro-magnet, used 
to produce the field in a dynamo or motor. 

Magnet, Haarlem. Celebrated magnets made in Haarlem, Hol- 
land. Logeman, Van Wetteren, Funckler and Van der Willigen 
were the makers who gave the celebrity to the magnets. They 
were generally horseshoe magnets, and would carry about twenty 
times their own weight. 

Magnet, Horseshoe. A magnet of U shape— properly one with 
the poles brought a little closer together than the rest of the limbs. 
For direct lifting and attractive effects it is the most generally 
adopted type. Its advantage as regards lifting effect is due to 
small reluctance, q. v., offered by a complete iron circuit, such as 
the armature and magnet together produce. As the term is now 
used it is applied to any U shaped magnet. 




Fig. 218. Joule's Electro-magnet. 

Magnet, Joule's Electro. An electro-magnet of the shape of 
a cylinder with a longitudinal segment cut-off. It is wound with 



338 STANDARD ELECTRICAL DICTIONARY. 

wire as shown. The segment cut-off is a piece of the same shape 
as the armature. It is of high power. 

Magnetic Adherence. The tendency of amass of iron to adhere 
to the poles of a magnet. It is best figured as due to the virtual 
shortening of lines of force, as the more permeable iron gives a 
better path for them than the air can afford, and consequently a 
virtually shorter one. 

Magnetic Attraction and Repulsion. The attraction of a mag- 
net for iron, steel, nickel and cobalt and of unlike poles of magnets 
for each other. It is identical with electro-magnetic attraction, 
q. v. (Also see Electro-magnetism.) 

Magnetic Attraction and Repulsion, Coulomb's Law of. 

Magnetic attraction and repulsion are inversely as the square of 
the distance. (Ganot.) 

While theoretically true in the case of isolated poles, in practise 
it does not generally apply on account of the large diameter and 
relative shortness of magnets. 

Magnetic Axis. The line connecting the poles of a magnet. It 
does not generally coincide exactly with any symmetrical axis of 
figure. In such cases an error is introduced into the indications of 
the needle which must be determined and allowed for in com- 
passes. To determine it with a magnetic needle the suspension cup 
is made removable, so that the needle can be reversed. Readings 
are taken with one side of the needle and then with the other side 
of the needle up, and the average corresponds with the position of 
the magnetic axis in both positions of the needle. 

Magnetic Azimuth. The angle, measured on a horizontal 
circle, between the magnetic meridian and a great circle of the 
earth passing through the observer and any observed body. It is 
the astronomical azimuth of a body referred to the magnetic 
meridian and therefore subject to the variation of the compass. The 
angle is the magnetic azimuth of the observed body. 

Magnetic Battery. A name for a compound permanent mag- 
net ; one made up by bolting or clamping together, or to single soft 
iron pole pieces, a number of single permanent magnets. There 
are a number of forms of compound magnets. In making them 
care has to be taken to have them of even strength. It is also well 
to have them slightly separated. The object of both these precau- 
tions is to prevent a stronger element or magnet from depolarizing 
its neighbor. 

Synonym — Compound Magnet. 

Magnetic Bridge. An apparatus for testing the relative per- 
meability of iron. It consists of a rectangular system of iron cores. 



STANDARD ELECTRICAL DICTIONARY. 



339 



Three of the sides are wound with wire as shown. The other side 
is built up of double bars, and from the centre two curved arms 
rise, as shown in the cut. The arms do not touch. Between them a 
short magnet is suspended by a filament, which also carries a 
mirror and an index. 




Fig. 219. Magnetig Bridge. 

A lamp and scale are provided as in the reflecting galvanometer. 
When adjusted the magnetic needle hangs as shown in the cut, 
Fig. 219, without any tendency to turn towards either curved pole 
piece. If all iron parts are symmetrical and of similar metal, a cur- 
rent through the coils will make no difference. It will work in 
magnetic opposition upon the two arms, or, in other words, will 
maintain both arms at identical potential. 

If there is the least difference in permeability, length or thick- 
ness between any of the iron bars the magnetic potential of the two 




Fig. 220. Pole Pieces, Magnetic Needle and Mirror of Magnetic Bridge. 

curved arms will differ, and the magnetic needle will turn one way 
or the other. In practical use different samples of iron are sub- 
stituted for the unwound members of the fourth side of the parallel- 
ogram, and the needle by its motions indicates the permeability. 

In the cut, Fig. 220, D D are the ends of the curved pole pieces ; 
A the wire carrying the mirror B and magnetic needle jY, and E is 
the index which shows the larger deflections. 



34o 



STANDARD ELECTRICAL DICTIONARY. 




Fig. 221. 



Magnetic Circuit. A magnetic field of force is characterized by 
the presence of lines of force, which, while approximately parallel, 

curve around and tend to form 
closed curves. The polarity 
of afield of force is referred 
to an imaginary direction of 
the lines of force from the 
north pole through space to 
the south pole, and in the 
part of the field corresponding 
to the body of the magnet, 
from the south to the north 
pole. The cut indicates these 
features. Hence the magnetic 
field of force is termed the 
magnetic circuit, and to it are 
attributed a species of resist- 
One-half Portion of a Double tprm^rl rplurtawrp n v 

Magnetic Circuit. an cetermea reluctance, q. y. , 

and the producing cause of the 
field or lines of force is termed sometimes magneto-motive force, 
q. v. , corresponding to the electro-motive force. The modern treat- 
ment of the magnetic circuit is similar to the application of Ohm's 
law and the laws of resistance and conductivity to the electric 
circuit. 

Magnetic Circuit, Double. A magnetic circuit which virtually 
represents two horseshoe magnets placed with their like poles in 
contact. It is used for field magnets, the armatures occupying a 
place between the consequent poles. 

Magnetic Concentration of Ores. The concentration of ores or 
the freeing them from their gangue by magnetic attraction. It is 
only applicable to those cases in which either the ore itself or the 
gangue is attracted by the magnet. Its principal application is to 
the concentration of magnetic iron sands. (See Magnetic Con- 
centration.) 

Magnetic Concentrator. An apparatus similar to a magnetic 
separator, q. v., but used to concentrate magnetic iron sands. By 
the action of electro-magnets the magnetic iron sand (magnetite) 
is separated from the sand with which it is mixed. 

Magnetic Conductivity and Conductance. The first notion 

of permeance and of the magnetic circuit included the idea of 

magnetic conductivity, which conducted lines of force urged by 

. magneto-motive force through a magnetic circuit. The terms are 

displaced by permeability and permeance. 

Magnetic Continuity. The completeness of a magnetic circuit, 
as when the armature of a horseshoe magnet is in contact with 



STANDARD ELECTRICAL DICTIONARY. 341 

both poles. It is an attribute of a paramagnetic substance only and 
is identical for permanent magnets or for electro-magnets. An 
air space intervening between armature and magnet poles, or a 
space filled with any diamagnetic substance prevents continuity, 
although the lines of force to some extent still find their way 
around. The leakage is increased by discontinuity. 

Magnetic Control. Control of a magnetic needle, magnet, 
iron index or armature, in a galvanometer, ammeter or voltmeter 
by a magnetic field ; the restitutive force being derived from a 
permanent magnet. 

Magnetic Couple. The couple of magnetic force which tends 
to bring the magnetic needle into the plane of the magnetic 
meridian. One force is represented by the imaginary pull upon the 
north pole, and the other by the opposite pull upon the south pole 
of the needle. The moment of the couple varies from a maximum 
when the needle is at right angles to the plane of the magnetic 
meridian to zero when it is in such plane. 

Magnetic Creeping. Viscous hysteresis ; the slow increase of 
magnetism in a paramagnetic body when exposed to induction. 




Fig. 222. Magnetic Curves or Figures. 
Magnetic Curves. The pictorial representation of magnetic 



342 STANDARD ELECTRICAL DICTIONARY. 

lines of force. It is generally produced by scattering filings on a 
sheet of paper or pane of glass held over a magnet. The filings 
arrange themselves in characteristic curves. Tapping the paper 
or pane of glass facilitates the arrangement, or jarring the filings off 
a smaller magnet, so that they fall polarized upon the paper, is 
thought by some to improve the effect. The group of curves forms 
what are termed magnetic figures, q. v. 

Magnetic Declination. The angular deviation of the magnetic 
needle, causing it to rest at an angle with the true meridian ; the 
variation of the compass. (See Magnetic Elements,) 

Magnetic Density. The intensity of magnetization expressed 
in lines of force per stated area of cross-section in a plane at right 
angles to the lines of force. 

Magnetic Dip. The inclination from the horizontal assumed by 
a magnetic needle free to move in the vertical plane. (See Magnetic 
Elements.) The angle of dip or inclination is entirely a function of 
the earth, not of the needle. 

Magnetic Discontinuity. A break or gap in a magnetic 
circuit. To make a complete circuit the iron or other core must 
be continuous. If the armature of a horseshoe magnet is in con- 
tact with both poles the continuity is complete. If the armature 
is not in contact magnetic continuity gives place to discontinuity. 
It is an attribute of a paramagnetic substance only, and is identical 
for permanent magnets, or for electro-magnets. 

Magnetic Elements. The qualities of the terrestrial magnetism 
at any place as expressed in its action upon the magnetic needle. 
Three data are involved. I. The Declination or Variation. II. 
The Inclination or Dip. III. The Force or Intensity. I. The 
Declination is the variation expressed in angular degrees of the 
magnetic needle from the true north and south, or is the angle 
which the plane of the magnetic meridian makes with that of the 
geographical meridian. It is expressed as east or west variation 
according to the position of the north pole ; east when the north 
pole of the needle is to the east of the true meridian, and vice versa. 
Declination is different for different places ; it is at present west 
in Europe and Africa, and east in Asia and the greater part of North 
and South America. The declination is subject to (a) secular, (b) 
annual and (c) diurnal variations. These are classed as regular ; 
others due to magnetic storms are transitory and are classed as 
irregular, (a) Secular variations. The following table shows the 
secular variations during some three hundred years at Paris. These 
changes are termed secular, because they require centuries for their 
completion. 



STANDARD ELECTRICAL DICTIONARY. 
Table of Declination or Variation, 



343 



Year. 


Declination. 


Year. 


Declination. 


Year. 


Declination. 


I 5 8o 


11° 30' E. 


1814 


22° 34' W. 


1855 


19° 57' W. 


1663 


o° 


1825 


22° 22 r W. 


i860 


19 32' W. 


1700 


8° io' W. 


1830 


22° I2 7 W. 


1865 


18 44' W. 


1780 


19° 55' W. 


1835 


22° 4' W. 


1875 


17 2l' W. 


1785 


22° OC/ W. 


1850 


20° 30 / W. 


1878 


1 7 oo / W. 


1805 


22° 5 7 W. 











On scrutinizing these figures it will be seen that there is part of a 
cycle represented and that the declination is slowly returning to 
the zero point after having reached its maximum western variation 
in 1814. Upwards of 300 years would be required for its comple- 
tion on the basis of what is known. In other places, notably the 
coast of Newfoundland, the Gulf of the St. Lawrence and the rest 
of the North American seaboard and in the British Channel, the 
secular variations are much more rapid in progress. (6) Annual 
variations — These were first discovered in 1780 by Cassini. They 
represent a cycle of annual change of small extent, from 15' to 18' 
only. In Paris and London the annual variation is greatest about 
the vernal equinox, or March 21st, and diminishes for the next three 
months, and slowly increases again during the nine following 
months. It varies during different epochs, (c) Diurnal variations 
w T ere discovered in 1722 by Graham. A long needle has to be 
employed, or the reflection of a ray of light, as in the reflecting galva- 
nometer, has to be used to observe them. In England the north pole 
of the magnetic needle moves every day from east to west from 
sunrise until 1 or 2 P. M. ; it then tends towards the east and 
recovers its original position by 10 P. M. During the night the 
needle is almost stationary. As regards range the mean amplitude 
of diurnal variations at Paris is from April to September 13' to 15' ; 
for the other months from 8' to io'. On some days it amounts to 
25' and sometimes is no more than 5 / '. The amplitude of diurnal 
variations decreases from the poles to the equator. Irregular varia- 
tions accompany earthquakes, the aurora dor ea lis and volcanic 
eruptions. In Polar regions the auroral variations may be very 
great; even at 40 latitude they may be i° or 2°. Simultaneous 
irregularities sometimes extend over large areas. Such are attrib- 
uted to magnetic storms. II. The Inclination is the angle which 
the magnetic needle makes with the horizon, when the vertical 
plane in which the needle is assumed to be free to move coincides 
with the magnetic meridian. It is sometimes called the dip of the 
needle. It varies as does the declination, as shown in the following 
table of inclinations of London. 



344 STANDARD ELECTRICAL DICTIONARY. 

Table of Inclination or Dip 



Year. 


Inclination. 


Year. 


Inclination. 


Year. 


Inclination. 


1576 


7i° 5o / 


1790 


7i° 33' 


1859 


68° 2l' 


1600 


72° 


1800 


70 35' 


1874 


67° 43' 


1676 


73° 3°' 


I82I 


70 31' 


1876 


67° 39'" 


1723 


74° 42' 


1828 


69 47' 


1878 


67° 36' 


1773 


72 19' 


1838 


69 \f 


1880 


67° 35' 


1780 


72 8' 


1854 


68° 31' 


188 1 


67° 35' 



III. Force or Intensity is the directive force of the earth. It 
varies with the squares of the number of oscillations the magnetic 
needle will make if caused to oscillate from a determined initial 
range. The intensity is supposed to be subject to secular change. 
According to Gauss the total magnetic intensity of the earth is 
equal to that which would be exerted if in each cubic yard there 
were eight bar magnets, each weighing one pound. This is, of 
course, a rough way of expressing the degree of intensity. Inten- 
sity is least near the magnetic equator and greatest near the mag- 
netic poles ; the places of maximum intensity are termed the 
magnetic foci. It varies with the time of day and possibly with 
changes in altitude. 

Magnetic Elongation. The elongation a bar of iron or steel 
undergoes when magnetized. By magnetization it becomes a little 
longer and thinner, there being no perceptible change in volume. 
The change is accompanied by a slight sound — the magnetic tick. 
An exceedingly delicate adjustment of apparatus is required for its 
observation. 

Magnetic Equator. A locus of the earth's surface where the 
magnet has no tendency to dip. It is, approximately speaking, a 
line equally distant from the magnetic poles, and is called also the 
aclinic line. It is not a great circle of the earth. 

Magnetic Field of Force. The field of force established by a mag- 
net pole. The attractions and repulsions exercised by such a field 
follow the course of the electro-magnetic lines of force. (See also 
Field of Force.) Thus the tendency of a polarized needle attracted 
or repelled is to follow, always keeping tangential to curved lines, 
the direction of the lines of force, however sweeping they may be. 
The direction of magnetic lines of force is assumed to be the direc- 
tion in which a positive pole is repelled or a negative one attracted; 
in other words, from the north pole of a magnet to its south pole in 
the outer circuit. The direction of lines of force at any point, and 
the intensity or strength of the field at that point, express the con- 



STANDARD ELECTRICAL DICTIONARY. 345 

ditions there. The intensity may be expressed in terms of that 
which a unit pole at unit distance would produce. This intensity 
as unitary it has been proposed to term a Gauss. (See Weber.) 

The direction of the lines of force in a magnetic field are shown 
by the time-honored experiment of sprinkling filings of iron upon 
a sheet of paper held over a magnet pole or poles. The\ T arrange 
themselves, if the paper is tapped, in more or less curved lines tend- 
ing to reach from one pole of the magnet to the other. Many 
figures may be produced by different conditions. Two near poles 
of like name produce lines of force which repel each other. (See 
Mag 11 et ic Cm rves . ) 

A magnetic and an electro-magnetic field are identical in all 
essential respects ; the magnetic field may be regarded as a special 
form of the electro-magnetic field, but only special as regards its 
production and its defined north and south polar regions. 

Synonym — Magnetic Spin (not much used). 

Magnetic Field, Uniform. A field of identical strength in all 
parts, such as the earth's magnetic field. If artificially produced, 
which can only be approximately done, it implies large cross-sec- 
tion of magnet pole in proportion to the length of the magnetic 
needle affected by it, which is used in determining its uniformity. 

Magnetic Figures. The figures produced by iron filings upon 
paper or glass held near magnetic poles. By these figures the 
direction of lines of force is approximately given, and a species of 
map of the field is shown. (See Magnetic Field of Force — Mag- 
netic Curves.) 

Magnetic Filament. The successive rows of polarized mole- 
cules assumed to exist in magnetized iron. Each molecule repre- 
sents an infinitely small magnet, and its north pole points to the 
south pole of the next molecule. Such a string or row is a theo- 
retical conception based on the idea that the molecules in a magnet 
are all swung into paralellism in the magnetizing process. A 
magnetic filament may be termed the longitudinal element of a 
magnet. (See Magnetism, Hughes' Theory of.) 

Magnetic Fluids. A two-fluid theory of magnetism has been 
evolved, analogous to the two-fluid theory of electricity. It 
assumes north fluid or "red magnetism" and a south fluid or 
11 blue magnetism." Each magnetism is supposed to predominate 
at its own pole and to attract its opposite. Before magnetization 
the fluids are supposed to neutralize each other about each mole- 
cule ; magnetization is assumed to separate them, accumulating 
quantities of them at the poles. 

Magnetic Flux. Magnetic induction ; the number of lines of 
force that pass through a magnetic circuit. 
Synonym — Magnetic Flow. 



346 STANDARD ELECTRICAL DICTIONARY. 

Magnetic Force. The forces of attraction and repulsion exer- 
cised by a magnet. By Ampere's theory it is identical with the 
forces of attraction and repulsion of electric currents. 

Magnetic Friction. The damping effect produced on the move- 
ments of a mass of metal by proximity to a magnet ; the phenom- 
enon illustrated in Arago's wheel, q. v. When a mass of metal 
moves in the vicinity of a magnet it cuts the lines of force emanat- 
ing from its poles, thereby producing currents in its mass ; as the 
production of these currents absorbs energy a damping effect is 
produced upon the movements of the mass. 

Magnetic Gear. Friction gear in which electro-magnetic ad- 
herence is employed to draw the wheels together. (See Adherence, 
Electro-magnetic — Electro-magnetic Friction Gear.) 

Magnetic Inclination. The inclination from the horizontal of 
a magnetic needle placed in the magnetic meridian. (See Mag- 
netic Element — Inclination Map.) 

Synonym — Magnetic Dip. 

Magnetic Induction. The force of magnetization within an 
induced magnet. It is in part due to the action of the surround- 
ing particles of polarized material ; in part to the magnetic field. 
(See Magnetic Induction , Coefficient of.) 

In a more general way it is the action of a magnet upon bodies 
in its field of force. In some cases the magnetism induced causes 
the north pole of the induced magnet to place itself as far as pos- 
sible from the north pole of the inducing magnet and the same for 
the south poles. Such substances are called paramagnetic or 
ferromagnetic. They lie parallel or tangential to the lines of 
force. In other cases the bodies lie at right angles or normal to 
the lines of force. Such bodies are called diamagnetic. 

Some bodies are crystalline or not homogeneous in structure, 
and in them the lines of magnetic induction may take irregular or 
eccentric paths. (See JEolotropic.) 

Synonym — Magnetic Influence. 

Magnetic Induction, Apparent Coefficient of. The apparent 
permeability of a paramagnetic body as affected by the presence of 
Foucault currents in the material itself. These currents act exactly 
as do the currents in the coils surrounding the cores of electro- 
magnets. They produce lines of force which may exhaust the per- 
meability of the iron, or may, if in an opposite direction, add to its 
apparent permeabilitv- 

Magnetic Induction, Coefficient of. The number, obtained 
by dividing the magnetization of a body, expressed in lines of 
force produced in it, by the magnetizing force which has produced 



STANDARD ELECTRICAL DICTIONARY. 347 

such magnetization, expressed in lines of force producible by the 
force in question in air. It always exceeds unity for iron, nickel 
and cobalt. It is also obtained by multiplying the coefficient of 
induced magnetization by /\it (4X3.14159) and adding 1. (See 
Magnetic Susceptibility — Magnetization, Coefficient of Induced.) 

The coefficient of magnetic induction varies with the material 
of the induced mass, and varies with the intensity of the magnetiz- 
ing force. This variation is due to the fact that as the induced 
magnetism in a body increases, the magnetizing force required 
to maintain such induction, increases in a more rapid ratio. The 
coefficient of magnetic induction is the same as magnetic perme- 
ability, and in a certain sense is the analogue of conductivity. It 
is also termed the multiplying power of the body or core magnet- 
ized. It is the coefficient of induced magnetization (see MagneU 
ization, Coefficient of Induced) referred to a mass of matter. For 
diamagnetic bodies the coefficient has a negative sign ; for para- 
magnetic bodies it has a positive sign. 

Synonyms — Permeability — Multiplying Power — Magnetic Induc- 
tive Capacity. 

Magnetic Induction, Dynamic. The induction produced by a 
magnetic field which moves with respect to a body, or where the 
body if moving moves at a different rate, or where the body moves 
and the field is stationary. In the case where both move, part of 
the induction may be dynamic and part static. (See Magnetic 
Induction , Static. ) 

Magnetic Induction, Static. Magnetic induction produced by 
a stationary field acting upon a stationary body. 

Magnetic Induction, Tube of. An approximate cylinder or 
frustrurn of a cone whose sides are formed of lines of magnetic 
induction. (See Magnetic Induction, Lines of.) The term tube is 
very curiously applied in this case, because the element or portion 
of a magnetic field thus designated is in no sense hollow or tubular. 

Magnetic Inertia. A sensible time is required to magnetize 
iron, or for it to part with its magnetism, however soft it may be. 
This is due to its magnetic inertia and is termed the lag. Perma- 
nent or residual magnetism is a phase of it. It is analogous to self- 
induction of an electric circuit, or to the residual capacity of a 
dielectric. 

Magnetic Insulation. Only approximate insulation of magnet- 
ism is possible. There is no perfect insulator. The best ones are 
only 10,000 times less permeable than iron. Hence lines of force find 
their way through air and all other substance, being simply crowded 
together more in paths of iron or other paramagnetic substance. 



348 STANDARD ELECTRICAL DICTIONARY. 

Magnetic Intensity. The intensity of the magnetization of a 
body. It is measured by the magnetic lines of force passing 
through a unit area of the body, such area being at right angles to 
the direction of the lines of force. 

Magnetic Lag. In magnetism the tendency of hard iron or steel 
especially to take up magnetism slowly, and to part with it slowly. 
(See Magnetic Inertia.) The lag affects the action of a dynamo, 
and is a minor cause of those necessitating the lead of the brushes. 

Synonym — Magnetic Retardation. 

Magnetic Latitude. Latitude referred to the magnetic equator 
and isoclinic lines. 

Magnetic Leakage. The lines of force in a field magnet which 
pass through the air and not through the armature are useless and 
represent a waste of field. Such lines constitute magnetic leakage. 

Magnetic Limit. The temperature beyond which a paramag- 
netic metal cannot be magnetized. The magnetic limit of iron is 
from.a red to a white heat ; of cobalt, far beyond a white heat ; of 
chromium, below a red heat ; of nickel at about 350 C. (662°F.) of 
manganese, from 15 C. to 20 C. (59 to 68° F.) 

Magnetic Lines of Force. Lines of force indicating the dis- 
tribution of magnetic force, which is due presumably to whirls of 
the ether. A wire or conductor through which a current is passing is 
surrounded by an electro-magnetic field of force, q. v., whose lines 
of force form circles surrounding the conductor in question. A 
magnet marks the existence of a similar electro-magnetic field of 




Fig. 223. Magnetic Lines of Force, Direction of. 

force whose lines form circuits comprising part of and in some 
places all of the body of the magnet, and which are completed 
through the air or any surrounding paramagnetic or diamagnetic 
body. They may be thought of as formed by the Amperian sheet of 
current, and analogous to those just mentioned as surrounding a 
conductor. 

A magnetic line of force may be thought of as a set of vortices 
or whirls, parallel to each other, and strung along the line of force 
which is the locus of their centres. 



STANDARD ELECTRICAL DICTIONARY. 349 

If as many lines are drawn per square centimeter as there are 
dynes (per unit pole) of force at the point in question, each such 
line will be a unitary c. g. s. line of force. 

Magnetic Mass. A term for a quantity of magnetism. Unit 
mass is the quantity which at unit distance exercises unit force. 

Magnetic Matter. Imaginary matter assumed as a cause of 
magnetism. Two kinds, one positive and one negative, may be 
assumedasin the two fluid theory of electricity, or only one kind, as 
in the single fluid theory of electricity. Various theories of 
magnetic matter have been presented whose value is only in their 
convenience. 

Magnetic Memory. The property of retaining magnetism ; 
coercive force ; magnetic inertia ; residual magnetism. 

Magnetic Meridian. A line formed on the earth's surface by 
the intersection therewith of a plane passing through the magnetic 
axis. It is a line determined by the direction of the compass 
needle. The meridians constantly change in direction and corre- 
spond in a general way to the geographical meridians. 

Magnetic Moment. The statical couple with wmich a magnet 
would be acted on by a uniform magnetic field of unit intensity if 
placed with its magnetic axis at right angles to the lines of force of 
the field. (Emtage.) 

A uniformly and longitudinally magnetized bar has a magnetic 
moment equal to the product of its length by the strength of its 
positive pole. 

Magnetic Needle. A magnet w T ith a cup or small depression at 
its centre and poised upon a sharp pin so as to be free to rotate or 
oscillate in a horizontal plane. The cup is often made of agate. 
Left free to take any position, it places its magnetic axis in the 
magnetic meridian. 

Magnetic Parallels. Lines roughly parallel to the magnetic 
equator on all parts of each of which the dip of the magnetic 
needle is the same ; also called Isoclinic Lines. These lines 
mark the places of the intersection of equipotential surfaces with 
the earth's surface. They are not true circles, and near the poles 
are irregular ellipses ; the magnet there points toward their centres 
of curvature. They correspond in a general way with the Geo- 
graphical Parallels of Latitude. 

Magnetic Permeability. The specific susceptibility of any sub- 
stance, existing in a mass, for magnetic induction. (See Magnetic 
Induction, Coefficient of, synonj-m for Magnetic Permeability 
and Mag 71 etiza tion , Coefficien t of In du ced. ) 

Sy7ionyms — Magnetic Inductive Capacity — Multiplying Power — 
Coefficient of Magnetic Induction. 



35o STANDARD ELECTRICAL DICTIONARY. 

Magnetic Perturbations. Irregular disturbances of the terres- 
trial magnetism, as by the aurora and in electric storms. 

Magnetic Poles. The points where the equipotential surfaces 
of the terrestrial field of force graze the earth's surface ; the points 
toward which the north or south poles of the magnetic needle is 
attracted. Over a magnetic pole the magnetic needle tends to 
stand in a vertical position. There are two poles, Arctic or nega- 
tive, and Antarctic or positive. Magnetic needles surrounding 
them do not necessarily point toward them, as they point to the 
centres of curvature of their respective magnetic parallels. The 
poles constantly change in position. The line joining them does 
not coincide with anything which may be termed the magnetic axis 
of the earth. 

Magnetic Poles, False. Poles on the earth's surface other 
than the two regular magnetic poles. There seem by observation 
to be several such poles, while analogy would limit true magnetic 
poles to two in number. 

Magnetic Potential. The potential at any point of a magnetic 
field is the work which would be done by the magnetic forces of 
the field upon a positive unit of magnetism as it moves from that 
point to an infinite distance. (Emtage.) 

Magnetic Proof Piece. A piece of iron used for testing mag- 
nets and the distribution of magnetism in bars, by suspending or 
supporting above or near the magnet, by detaching after adherence, 
and in other ways. 

Magnetic Proof Plane. An exploring coil used for testing the 
distribution of magnetism. It is connected in circuit with a 
galvanometer, and exposed to alternation of current, or to other 
disturbing action produced by the magnet or field under examina- 
tion. This affects the galvanometer, and from its movements the 
current produced in the coil, and thence the magnetic induction 
to which it was exposed, are calculated. 

Synonym — Exploring Coil. 

Magnetic Quantity. The magnetism possessed by a body ; it is 
proportional to the action of similar poles upon each other, or to 
the field produced by the pole in question. It is also called the 
strength of a pole. 

The force exercised by two similar poles upon each other varies 
with their product and inversely with the square of the distance 
separating them ; or it may be expressed thus (mXm) -V L 2 . This 
is a force, and the dimensions of a force are ML/T 2 . Therefore, 
w 2 /L 2 = ML/T 2 orm = M^L f /T. 



STANDARD ELECTRICAL DICTIONARY. 351 

Magnetic Reluctance. The reciprocal of permeance ; mag- 
netic resistance ; the relative resistance to the passage of lines of 
force offered by different substances. The idea is derived from 
treating the magnetic circuit like an electric one, and basing its 
action on magneto-motive force acting through a circuit possess- 
ing magnetic reluctance. 

Magnetic Reluctivity. The reciprocal of magnetic permea- 
bility, q. v. 

Synonym — Magnetic Resistance. 

Magnetic Retentivity. The property of steel or hard iron by 
which it slowly takes up and slowly parts with a magnetic con- 
dition — traditionally (Daniell) called coercitive force. 

Magnetic Rotary Polarization. If a plane polarized beam of 
light is sent through a transparent medium in a magnetic field 
its plane of polarization is rotated, and this phenomenon is denoted 
as above. (Compare Refraction , Electric, and see Electro-magnetic 
Stress.) This has been made the basis of a method for measuring 
current. A field of force varies with the current ; the polarization 
produced by such field is therefore proportional to the current. 
(Becquerel & Rayleigh.) 

A plane polarized beam of light passing through the transparent 
medium in the magnetic field by the retardation or acceleration of 
one of its circular components has its plane of polarization rotated 
as described. The direction of the lines of force and the nature of 
the medium determine the sense of the rotation ; the amount 
depends upon the intensity of the field resolved in the direction of 
the ray, and on the thickness and nature of the medium. 

Magnetic Saturation. The maximum magnetic force which 
can be permanently imparted i.o a steel bar. A bar may be mag- 
netized beyond this point, but soon sinks to it. The magnetism 
produced in a bar is prevented from depolarization by the retentivity 
or coercive force of the bar. The higher the degree of magnetiza- 
tion the greater the tendency to depolarization. 

It is also denned as the maximum intensity of magnetism pro- 
duced in a paramagnetic substance by a magnetic field as far as 
affected by the permeability of the substance in question. The 
more lines of force passed through such a substance the low T er is its 
residual permeability. It is assumed that this becomes zero after a 
certain point, and then the point of saturation is reached. After 
this point is reached the addition of any lines of force is referred 
entirely to the field and not at all to the permeability of the sub- 
stance. But such a zero is only definable approximately. 

Magnetic Screen. A box or case of soft iron, as thick as prac- 
ticable, for protecting bodies within it from the action of a magnetic 



352 



STANDARD ELECTRICAL DICTIONARY. 



field. The lines of force to a great extent keep within the metal of 
the box on account of its permeability, and but a comparatively 
few of them cross the space within it. 

Such screens are used to prevent watches from being magnetized, 
and are a part of Sir William Thomson's Marine galvanometer. 

A magnetic screen may be a sphere, an infinite or very large 
plane, or of the shape of any equipotential surface. 

Synonym — Magnetic Shield. 

Magnetic SehMnduction. The cause of a magnet weakening 
is on account of this quality, which is due to the direction of the 
lines of force within a magnet from the positive towards the neg- 
ative pole. " A magnet thus tends to repel its own magnetism and 
to weaken itself by self-induction." (Daniell.) 

Magnetic Separator. An apparatus for separating magnetic 
substances from mixtures. Such separators depend on the action 
of electro-magnets. In one form the material falls upon an iron 

drum, magnetized by coils. Any 
magnetic substance adheres to the 
drum and is thereby separated. 
They are used by porcelain makers 
for withdrawing iron particles from 
clay, by machinists to separate iron 
filings and chips from brass , and for 
similar purposes. 

Magnetic Shell. A theoretical 
conception of a cause of a magnetic 
field or of a distribution of magnet- 
ism. If we imagine a quantity of 
very short magnets arranged in 
contact with their like poles all 
pointing in the same direction so as 
to make a metal sheet, we have 
a magnetic shell. Its magnetic 
moment is equal to the sum of the 
magnetic moment of all its parts. 
If the shell is of uniform strength the magnetic moment of a unit 
area gives the strength of the shell ; it is equal to the magnetic 
quantity per unit of area, multiplied by the thickness of the shell. 
If its strength is uniform throughout a magnetic shell is called 
simple ; if its strength varies it is termed complex. 

Emtage thus defines it : A magnetic shell is an indefinitely thin 
sheet magnetized everywhere in the direction normal to itself. 

Magnetic Shell, Strength of. The magnetic quantity per unit 
of area of the shell multiplied by the thickness of the shell. 




Fig. 224. Magnetic Separator. 



STANDARD ELECTRICAL DICTIONARY. 



353 



Magnetic Shield. In general a magnetic screen, q. v. Some- 
times a strong local field is made to act as a shield, by its predomi- 
nance overcoming any local or terrestrial field to which the needle 
to be protected may be exposed. 

Magnetic Shunt. The conception of a magnetic circuit being 
formed, the shunt is a corollary of the theory. It is any piece of 
iron which connects points of a magnet differing in polarity, so as 
to divert part of the lines of force from the armature or yoke. The 
shunt is especially applicable in the case of horseshoe magnets. 
Thus a bar of iron placed across from limb to limb a short distance 
back from the poles would act as a shunt to the armature and 
would divert to itself part of the lines of force which would other- 
wise go through the armature and would weaken the attraction of 
the magnet for the latter. In dynamos a bar of iron used as a 




Fig. 225. Magnetic Shunt. 

magnetic shunt has been used to diminish the lines of force going 
through the armature and hence to weaken the field and diminish 
the electro-motive force. By moving the shunt nearer or further 
from the poles the dynamo is regulated. 

In the cut the projections between the yoke and poles of the 
magnet shown act as a shunt to the yoke, taking some lines of 
force therefrom. 

Magnetic Storms. Terrestrial magnetic disturbances some- 
times covering very wide areas, and affecting the magnetic declin- 



354 STANDARD ELECTRICAL DICTIONARY. 

ation and inclination. One such disturbance was felt simultane- 
ously at Toronto, Canada, the Cape of Good Hope, Prague and 
Van Diemen's Land. (Sabine.) 

Magnetic Strain. The strain produced by magnetic lines of 
force in substances exposed to their action. It is observed in 
substances placed between the poles of a strong electro-magnet, 
and evinces itself in the alteration of the optical properties of 
transparent substances. 

Magnetic Stress. The stress produced by magnetic lines of 
force on substances through which they pass, evidenced in altera- 
tion of the optical properties of transparent bodies thus treated. 

Magnetic Susceptibility. The specific intrinsic susceptibility 
of any material for magnetic induction. It refers to the particle of 
matter, and not to the mass, as in the latter its own particles react 
on each other and bring about what is termed permeability, q. v. 
(See also Magnetization, Coefficient of Induced, and Magnetic 
Induction, Coefficient of.) 

Synonym — Coefficient of Induced Magnetization. 

Magnetic Tick. When a bar of iron is suddenly magnetized 
or demagnetized it emits a slight sound, called the Page sound, or 
the magnetic tick. This has been utilized in a telephone by Reiss. 
The telephone will receive sound, but is very weak. It consists of 
a bar surrounded with a coil of insulated wire. Variations in cur- 
rent produce sounds, which maybe articulate if the currents are 
produced by a telephonic transmitter. 

Magnetic Twist. A bar of iron held in the magnetic meridian 
and pointing to the pole and twisted becomes to some extent 
permanently magnetized. Conversely a bar when magnetized 
seems to have a twist set up in it. The latter is magnetic twist. 

Magnetic Variations. Changes in the value of magnetic 
declination or inclination. (See Magnetic Elements.) 

Magnetism, Ampere's Theory of. A theory accounting for 
magnetic phenomena by assuming the existence of currents circu- 
lating around the molecules of permanent magnets. If such cur- 
rents so circulate and all in the same direction, the result is the 
same as if the body of the magnet was enveloped in currents repre- 
senting those of an electro-magnet or solenoid. This is because in 
the interior the current around one molecule would counteract the 
current around its neighboring ones in part, so that the only vir- 
tual currents left would be represented by those on the outer sur- 
faces of the outer shell of molecules, and these virtually resolve 
themselves into one general current sheet, surrounding the mag- 
net and coinciding with its surface. 



STANDARD ELECTRICAL DICTIONARY. 



355 



The theory assumes that such currents permanently circulate 
around the molecules of paramagnetic substances. Under ordinary 
conditions there is no coincidence in their direction and no 




Amperian Currents in Magnets. 



resultant current is produced. When magnetized or polarized the 
molecules are brought into order, so that the direction of their cur- 
rent coincides and the body becomes a magnet. 

At the north pole of the magnet the direction of the Amperian 
currents is the reverse of that of a watch when the observer faces 
the pole ; the reverse obtains for the south pole. 

The attraction of opposite and repulsion of similar poles is 
explained by the actions of the Amperian currents upon each 
other. If north and south pole are placed together these currents 
will coincide in direction and hence will attract each other. If 
two like poles are put together the currents will have opposite 
directions and will repel each other. 

No energy is supposed to be required to maintain currents 
around or in a single molecule. 





North and South Poles of a Magnet Showing 
Direction of Amperian Currents. 

Magnetism, Blue. A term arising from the two fluid theory of 
magnetism ; the magnetism of the south pole of a magnet. (See 



356 STANDARD ELECTRICAL DICTIONARY. 

Magnetic Fluids.) The magnetism of the north pole is termed 
red magnetism. Both terms originated presumably in the paint- 
ing of magnets, and are little used. 
Synonym — South Magnetic Fluid, 

Magnetism, Components of Earth's. The magnetic force of 
the earth acts in the plane of the magnetic meridian and in direc- 
tion generally lies oblique to the plane of the horizon. It can be 
resolved into two components, one vertical, which has no directive 
effect upon the magnetic needle, the other horizontal, which repre- 
sents the directive element for the usual compass needle. For the 
dipping needle, q. v., the vertical component is the only active one. 
a. magnetic needle mounted on a universal joint at its centre of 
gravity would be acted on by both components. 

Magnetism, Creeping of. The gradual increase of magnetism 
when a magnetic force is applied with absolute steadiness to a 
piece of iron. It is a form of magnetic lag. It may last for half an 
hour and involve an increase of several per cent, of the total mag- 
netism. 

Synonym — Viscous Hysteresis. 

Magnet, Iron Clad. A magnet with a casing of iron connected 
at one end to the core. The term is generally applied to electro- 
magnets of this form. 

Synonyms — Tubular Magnet — Jacketed Magnet. 

Magnetism, Decay of. The gradual loss of magnetism by per- 
manent magnets, due to accidental shocks, changes of temperature, 
slow spontaneous annealing of the iron and other similar causes. 

Magnetism, Discharge of. The loosing of magnetization. 
Thus in a shunt-wound dynamo there is a critical resistance for 
the outer circuit, below which the field ceases to be magnetized, as 
enough current ceases to be shunted into it to magnetize it. The 
machine is said to unbuild itself, and a discharge of magnetism 
occurs from the field magnet. 

Magnetism, E wing's Theory of. Ewing found by a model 
consisting of a number of pivoted magnetic needles that the 
observed phenomena of magnetization could be represented thereby. 
Thus there would be no need of assuming internal frictional forces 
of Maxwell, nor the closed rings or chains of Hughes. The theory 
retains the notion, however, of paramagnetic matter, consisting of 
an assemblage of molecular magnets. The loss of energy by 
hysteresis is represented in the model by the energy lost by the 
needles in beating against the air. 

Magnetism, Free. The magnetism or magnetic field outside 
of a magnetic circuit. It is due to escape of lines of force and to the 



STANDARD ELECTRICAL DICTIONARY. 357 

magnetic leakage through the air. The lines of force are never, 
under the most favorable circumstances, confined to the metallic 
circuit of the magnet and armature. In a simple magnet without 
armature all the lines of force have to follow an air path, and the 
field is at its strongest. As the magnetism is strongest at the sur- 
face near the poles, the term is sometimes understood as applying 
to the surface attraction. In such case it is defined as the distribu- 
tion, on a magnetized bar or mass, of magnetic lines of force as 
they emerge from its surface. 

Synonym — Surface Magnetization. 

Magnetism, Hughes' Theory of. A theory accounting foi 
magnetic phenomena by assuming that each molecule is a magnet, 
and that in a polarized or magnetized body they are all arranged 
with their poles in the same direction, while in an unmagnetized 
body their poles, alternating in direction, neutralize each other. 

Magnetization consists in a partial rotation of the molecules so as 
to make them agree in position, thus, as a resultant developing 
north and south poles at the ends of the bar. 

The theory is in a certain sense simpler than Ampere's theory, 
but is not so generally adopted. 

Magnetism, Lamellar Distribution of. The distribution of 
magnetism in thin and uniform or " simple magnetic shells," q. v. 
A given distribution is termed lamellar if the substance in which it 
exists can be divided into simple magnetic shells, which either 
form closed surfaces, or have their edges in the surface of the sub- 
stance. In lamellar distribution the polar area is very large com- 
pared with the distance between opposite poles. 

Magnetism of Gases. Faraday experimented on this point by 
coloring gases with a little vapor of iodine or other colored gas, 
and letting them flow between the two poles of a powerful electro- 
magnet. In this way he 'found some are repelled, some attracted, 
and in the case of oxygen, it is attracted at one temperature and 
repelled at another. At ordinary temperatures a cubic yard 
of oxygen possesses the magnetism of 5.5 grains of iron and when 
liquefied it is strongly attracted. 

Magnetism or Magnetization, Temporary. When a mass of 
iron is magnetized by a current, when the current ceases the portion 
of its magnetism which disappears is the temporary magnetism ; 
the portion retained is the residual or permanent magnetism. 

Magnetism, Red. A term arising from the two fluid theory of 
magnetism ; the magnetism of the north pole of a magnet. (See 
Magnetic Fluids.) The magnetism of the south pole is termed 
blue magnetism. Both terms originated in the painting of mag- 
nets. They are but little used. 

Synonym — North Magnetic Fluid. 



358 STANDARD ELECTRICAL DICTIONARY. 

Magnetic Remanence. The residual magnetism left in a bar 
of steel or other paramagnetic material after the application of a 
powerful magnet. It is distinguished from coercive force, as the 
latter is the amount of negative magnetizing or of demagnetizing 
force required to reduce the remanent magnetism to zero. 

Synonym — Remanence — Residual Magnetism. 

Magnetism, Solenoidal Distribution of. The distribution of 
magnetism in such a way that the poles are very far apart in pro- 
portion to their area. The magnetization of a long thin bar of 
steel illustrates solenoidal distribution. 

Magnetism Sub=permanent. The magnetism of a paramagnetic 
substance which presents a considerable degree of permanency, but 
which gradually dissappears, leaving the permanent magnetism 
present. It is noticeable in iron or steel ships whose magnetism 
gradually reduced in quantity, eventually becomes fully permanent. 

Magnetism, Weber's Theory of. The molecules of a magnetiza- 
ble material by this theory are supposed to be magnets with their 
poles lying in every direction, and hence neutralizing each other. 
By magnetization these are supposed to be turned with their simi- 
lar poles in the same direction, and their axis parallel, hence acting 
like a group of magnets. It is practically identical with Hughes' 
theory. 

Magnetism, Terrestrial. The magnetism of the earth. (See 
Magnetic Elements.) 

Magnetization by Double Touch. The process of magnetizing 
a steel bar by simultaneously stroking it with two poles of a horse- 
shoe magnet or with two opposite poles of two bar magnets. The 
poles must be close but not touching. A block of wood may be 



Fig - . 228. Magnetization by Double Touch. 

placed between the ends if single magnets are used. The poles are 
placed on the middle of the bar and carried back and forth to one 
end, then to the other, and so on, ending at the middle of the bar in 
such direction as to give each end the same number of strokes. 
The poles must be close together or consequent poles will be pro- 
duced. If bar magnets are used they may be held inclined at an 
angle of 15 ° to 20 with the horizontal bar to be magnetized. The 
ends of the latter may rest on poles of two other magnets, each end 



STANDARD ELECTRICAL DICTIONARY. 359 

on a pole of the same name as that of the magnetizing magnet on 
its side. (See Magnetization, Hoffer's Method.) 

Magnetization by Separate Touch. A method of magnetiza- 
tion. Two magnets are used. Held in an inclined position two 
opposite poles are touched to the bar near its centre, and are drawn 
off to the two ends. They are returned through the air and the 
process is repeated. 

Magnetization by Single Touch. A method of polarizing or 
magnetizing steel bars, by stroking them always in one direction 
with one pole of a magnet, returning it through the air. The 
stroking is best done on both sides. The stroking may begin at 
one end ana end at the other, or it may be commenced in the center 
of the bar and be carried to one end with one pole, and the same 
done for the other half with the other pole. 

Magnetization by the Earth. The earth imparts magnetism 
to iron masses. If a rod of steel is held parallel to the inclination 
and in the magnetic meridian it exhibits polarity, which by jarring 
or hammering, can be made to some extent permanent. A piece 
of soft iron held vertically, or still better in the line of the dip as 
above, and which is twisted when in that position, becomes mag- 
netized with some degree of permanence. Many other instances 
are cited, such as fire-irons, lamp-posts, iron gates, lathe turnings, 
all of which often exhibit polarity, having been magnetized by the 
earth's field. 

Magnetization, Coefficient of Induced. The coefficient (q. v.) 
expressing the relation between the specific intensity of magneti- 
zation of a particle and the magnetizing force. The magnetizing 
force is measured by the lines of force it can produce in a field of 
air. The coefficient of induced magnetization is the factor by 
which the intensity of a magnetizing field must be multiplied to 
produce the magnetization imparted by it to a particle of any sub- 
stance. This coefficient varies for different substances, and is also 
called magnetic susceptibility. It is distinguished from permea- 
bility as referring only to a particle isolated from influence of a 
mass of surrounding particles of its own kind. It is definable as the 
intensity of the magnetization assumed by an exceedingly long and 
exceedingly thin bar placed in a unit field. If a mass of metal 
were placed in such a field all its particles would become affected 
and within the mass no unit field could exist. Hence magnetic 
susceptibility (another name for this coefficient) does not apply to 
the case of large cores of electro-magnets and dynamo-armatures, 
but is really a theoretical rather than a practical figure. 

The sign of the coefficient of diamagnetic bodies is negative ; of 
paramagnetic bodies is positive. 

Synonym — Magnetic Susceptibility. 



360 



STANDARD ELECTRICAL DICTIONARY. 



Magnetization, Cycle of. A cycle of positive or of positive and 
negative magnetization represents the application of a magnetizing 
force beginning at a fixed value, generally zero, rising to a maxi- 
mum, or to a value of maximum distance from the initial and then 
returning to the original basis. It is virtually a full wave of mag- 
netization and may extend on both sides of a zero line giving 
positive and negative values. 

Cycles of magnetization apply especially to transformers and 
other apparatus of that character used with the alternating current 
system. 

Magnetization, Hoffer's Method. For horseshoe bars an arma- 
ture is placed against the poles of the magnet bar to be treated. 
The poles of a strong horseshoe magnet are stroked over it from 
poles to bend and returned through the air, or vice versa. In the 
first case the poles will be the same as those of the inducing mag- 
net ; in the second case they will be opposite. A maximum effect 
is produced in ten strokes. The stroking should be applied to 
both sides. An electro-magnet may be used as inducer as shown, 
but an armature should be used ; in the cut it is omitted. 




Fig. 229. Magnetizing a Horseshoe Magnet. 

Magnetization, Intensity of. The amount of magnetism in- 
duced in or present in a body. It is expressed in Magnetic Lines 
of Force, q. v., per cross-sectional area. 

Magnetization, Isthmus Method of. A method used by Ewing 
in a research on the magnetization of iron in very strong fields. 
He used samples of iron turned down in the centre to a narrow 
neck, and thus concentrated the lines of force greatly. 

Magnetization, Elias' Method. The bar to be magnetized is 
surrounded by a magnetizing coil, q. v. A strong current is passed 
through it, and the coil is moved back and forth a few times. 

Magnetization, Jacobi's Method. For horseshoe bars. The 
bar is placed with its poles against those of a horseshoe magnet. 
A bar of soft iron, long enough to reach from outside to outside of 



STANDARD ELECTRICAL DICTIONARY. 361 

the legs, is laid across near the junction and is drawn along towards 
the bend of the new bar and away from it. This is repeated a few 
times on both sides. 

Magnetization, Limit of. As the induction of magnetizing 
force increases, magnetization of paramagnetic metals tends towards 
a limit, the increase in magnetization being continually less and 
less as the metal becomes more highly magnetized. In diamag- 
netic substances no limit is discernible. 

Synonym — Maximum Magnetization. 

Magnetization, Specific. The magnetic moment per gram of a 
substance. 

Magnet=keeper. A bar of iron connecting the two poles of a 
permanent magnet. Often the same bar serves as armature and 
keeper. 

Magnet, Lamination of. It is advantageous to make magnets 
of laminated construction, or of thin plates of steel. The thin 
metal can be better tempered or hardened than thick metal. A 
slight separation of the plates is advantageous from some points of 
view. If in actual contact there is some danger that the weaker 
members will have their polarity reversed by the stronger ones. 
This is counteracted to some extent by separation. 

Magnet, Long Coil. A high resistance electro-magnet ; one 
whose coil is of thin wire of considerable length. 

Magnet, Natural. The lodestone, q. v.; a variety of magnetite 
or magnetic oxide of iron, exhibiting permanent magnetism, attract- 
ing iron, and possessing north and south poles. 

Magnet, Neutral Line of. A line at right angles to the mag- 
netic axis of a magnet, q. v., and nearly or quite at the centre, so 
situated with reference to the poles on either end that it marks the 
locus of no polarity. It has been called the equator of the magnet. 
It is denned by the intersection of the plane of no magnetism with 
the surface of the bar. 

Synonym — Magnetic Equator. 

Magnet, Normal. A bar or compound bar magnet, magnetized 
to such an extent that the curves of the lines of force run into each 
other in the middle, is thus termed by Jamin. 

Magneto. Abbreviation for Magneto-electric Generator. (See 
Magneto-electric Generator.) 

Magneto Call Bell. A call operated by current from a magneto- 
electric generator. It is very generally used in telephone systems. 

Magneto=electric. adj. Relating to induced electric effects due 
to the cutting of true magnetic lines of force by, or equivalent 



362 



STANDARD ELECTRICAL DICTIONARY. 



action of or upon a conductor. These effects are identical with 
electro-magnetic effects and are only distinguished from them by 
the field being due to a permanent magnet instead of an electro- 
magnet. 

Magneto=electric Brake. A device for bringing to rest an 
oscillating galvanometer needle. It consists essentially of a coil in 
circuit with a key and with the galvanometer. On opening the 
circuit an inverse current is established by induction, tending to 
bring the needle to rest. 

Magneto=electric Generator. A current generator operating 
by maintaining a potential difference at its terminals, by reactions 
in a field of force, which field is established by a permanent magnet. 




Fig. 230. Magneto-Electric Generator. 



The cut, Fig. 230, shows the general principle of construction 
of a direct current generator. The armature is rotated between 




Fig. 231. Magneto-Electric Generator. 
the poles of a permanent magnet. Any of the regular types of 
dynamo armature can be used. From its commutator the current 
is taken by brushes. 



STANDARD ELECTRICAL DICTIONARY. 



363 



The cut, Fig. 231, shows an alternating current machine. In it 
a pair of bobbins, wound in series, and both either right-handed or 
left-handed, are rotated between permanent magnet poles. The 
current may be taken off by two brushes bearing on two collecting 
rings on the axis of the bobbins, the ends of the wire being con- 
nected thereto. Or if a shocking current is desired, one of the 
brushes or springs may strike a series of pins forming virtually a 
broken or interrupted collecting ring. This gives a current for 
medical purposes. 

Synonyms — Magneto-dynamo — Magneto-electric Machine. 

Magnetograph. An apparatus for recording variations in mag- 
netic elements. 

One type includes a magnetic needle to which a concave mirror 
is attached. The light ray from the mirror is reflected upon sensi- 
tized paper where its movements are photographically reproduced. 
The movements of the spot are due to the movements of the needle 
and act as the record of the same. 

Magneto=Inductor. An in- 
strument for use with a ballistic 
galvanometer to reproduce a 
definite current impulse. Two 
magnets are fastened together 
in one straight line, the north 
poles almost touching. This is 
mounted at the end of a rod like 
a pendulum, the axis of the 
magnets transverse to the rod. 
The magnets are carried by a 
frame and oscillate at the end of 
the rod, back and forth within 
a fixed coil, which is one-half 
the length of the double magnet. 
A bob is attached to the bottom 
of the frame by which the whole 
can be swung. As the magnets 
are of fixed value, their time of 
oscillation constant, and the 
coil fixed in size, the apparatus 
provides a means of getting a 
definite instantaneous current 
of identical value whenever 
needed. 

Magnetometer, (a) A re- 
flecting galvanom et e r , with 

heavy magnetic needle, dampened by a copper frame. 
devised by Weber. 




Magneto-Inductor. 



It was 



3^4 



STANDARD ELECTRICAL DICTIONARY. 



(6) An apparatus for measuring the intensity of magnetic force. 
It may consist of a magnet suspended by bifilar or by torsion sus- 
pension. A reflecting mirror and scale as in the reflecting galva- 
nometer may be used to act as indicator of its motions. It is used in 
investigations of the intensity of the earth's field. 

If the motions of the spot of light are received on a moving strip 
of sensitized paper and are thereby reproduced photographically, 
the instrument is self-recording. Such an apparatus is used in the 
Kew Observatory, Eng., for recording the terrestrial magnetic 
elements. 

Magnetometry. The determination of the magnetic moment 
of a magnet. 

It involves the determination by experiment of — (a) the 
product of the magnetic moment, M, of the magnet by the hori- 
zontal component, H, of the earth's magnetism ; (6) the quotient 
of M divided by H. Knowing these two quantities, M is given by 
the formula M^^/MHXM/H and if desired H is given by the 
formula H = /MH-fM/H. 

M H is determined by the method of vibrations. A very long, 
thin magnet suspended by a torsion filament is caused to oscillate, 




- fegfei 




Fig. 



Broadside Method. 



233. End-on Method. 

and its period is determined. Calling such period T and the 
m oment of inertia of the magnet I, we have the formula T= 2 it 
|/I/HM (a), whence H M is calculated, I of course being known 
or separately determined. 

M/H is determined by the End-on deflection method, or the 



STANDARD ELECTRICAL DICTIONARY. 365 

Broadside deflection method. In both cases the deflection of a 
compass needle by the magnet in question is the basis of the work. 

In the end-on method S N is the magnet under examination ; s n 
the compass needle ; a the angle of deflection ; d the distance 
between O and the middle of S N, which should be considerable 
compared with the length of 5 n ; 2/ the length of S N. We then 
have the formula tan a = M H X 2ci ; (d 2 -l-) 2 y which if 2/ is small 
compared to d reduces to tan a = M/Hrf 3 (b) t which gives M/H, a 
and d being known. 

In the broadside method the line d is the magnetic meridian, 
and the diagram shows the relative positions. We then have the 
formula tan a = M/H X i/(flT 2 +/ 2 )f ; which if/ is relatively small 
reduces to tan a = M/Ha? (c. ) 

a and c or a and b can be combined giving M and H in C. G. S. 
measurement. 

Magnetometer, Differential. An apparatus, invented by 
Eickemeyer, for testing the magnetic qualities of different samples 
of iron. It is very similar in construction and principle to the 
magnetic bridge, q. v. 

Magneto=motive Force. The force producing a magnetic field 
or forcing lines of force around a magnetic circuit. It is usually 
applied only to electro-magnets and is 
expressible in turns of the wire winding 
multiplied by amperes of current, or in 
ampere-turns. 

Magnet Operation . A term in surgery ; 
the use of the electro-magnet or permanent 
magnet for removing particles of iron from 
the eye. 

Magnetoscope. An apparatus for de- 
tecting the presence of magnetism, without 
measuring its intensity. A simple mag- 
neto-scope consists of a magnetized bit of 
watch-spring suspended in a vertical glass 
tube by a fine filament. A bit of unmag- 
netized soft iron wire may be used in the 
same way. The first has the advantage 
of indicating polarity ; the latter merely 
shows magnetic attraction. A cork may 
be used as base of the instrument. 

Magnet, Permanent. A bar of steel 
charged with residual magnetism. Steel Fl %- 2 35- Magnetoscope. 
possesses high coercive force in virtue of 
which when once magnetized it retains part of the magnetization. 




366 STANDARD ELECTRICAL DICTIONARY. 

Permanent magnets are generally straight bars or U shaped ; 
they are termed bar magnets, magnetic needles, horseshoe mag- 
nets, machine magnets and otherwise, according to their shape or 
uses. 

Magnet Pole. The part of a magnet showing strongest polarity ; 
the part which attracts iron the most powerfully, and acts as the 
starting point for lines of force. 

Magnet Poles, Secondary. Magnet poles are often not situated 
at the ends. Owing to inequality of the material or other causes 
they may occupy intermediate positions on the magnet. Such 
poles are called secondary poles. 

Magnet Pole, Unit. A unit magnet pole is one which exerts 
unit force on another unit pole placed at unit distance from it. 
Unit force is the dyne ; unit distance is one centimeter. 

Magnet, Portative Power of. The power of sustaining a 
weight by attraction of its armature possessed by a magnet. In 
general terms the adherence of the armature of a magnet to the pole 
varies with the square of the number of lines of force which pass 
through the point of contact. Hence an increased adherence of 
the armature to a horseshoe electro-magnet is sometimes obtained 
by diminishing the area of contact of one pole which concentrates 
the lines of force. Steel magnets were frequently made with 
rounded ends to increase the portative power. 

Magnet, Simple. A magnet made of one piece of metal, or at 
least magnetized as such ; the reverse of a compound magnet, which 
is magnetized piece by piece and then fastened together. 

Magnet, Solenoidal. A magnet which is so uniformly magnet- 
ized and is so long in proportion to its other dimensions that it 
virtually establishes two magnetic poles, one at either end. It is a 
long thin bar so magnetized that all its molecules would, considered 
as magnets, be absolutely equal. (Daniell.) It acts like a solenoid, 
except that it is longer in proportion than the solenoid generally is 
constructed. 

Magnet, Sucking. A magnet coil with movable or loose axial 
bar of soft iron. 

The whole is usually mounted vertically. When a strong 
enough current is passed the bar is drawn up into the coil as if by 
suction, whence the name. 

Magnet, Unipolar. No such thing as a unipolar magnet is pos- 
sible. The name is given to poised or suspended magnets, one of 
whose poles lies in the axis of suspension. It is obvious that such 
a magnet will act, as far as its directive tendency and rotatory 




STANDARD ELECTRICAL DICTIONARY. 367 

movements are concerned, as if it had only one pole. As shown 
in the cut, the pole s in both mag- 
nets lies in the axis of suspension 
or directly under the filament by 
which they are suspended, while 
the other pole n is the active pole 
in causing rotation or directive 
tendency ; c c are counterweights 
or counterpoises. 

Magnetophone. An apparatus 
for producing a loud sound, involv- 
ing the principles of the telephone. 
A rapidly alternating or make and Fig. 236. Unipolar Magnets. 
break current being produced by 

any means and being transmitted through the telephone gives a 
loud note of pitch dependent on the current producing it. Some- 
times a perforated metallic disc is rotated in a magnetic field, and 
produces the requisite type of current. 

Magnus' Law. A law of thermo-electricity. In a homogeneous 
circuit, however, the temperature varies from point to point ; there 
is no current. 

Whatever potential differences may be established by the varia- 
tions in temperature it is evident that they must counteract each 
other and reduce to zero. 

Mains, Electric. The larger conductors in a system of electric 
light or power distribution. 

Make. v. To complete a circuit, as by closing a switch. 

Make and Break Current. A current which is continually 
broken or interrupted and started again. It is applied only where 
the "makes" and "breaks" succeed each other with great rapidity, 
as in the action of an induction coil or pole changer, etc. It 
has had considerable importance in litigation affecting the Bell 
telephone patents, the courts holding that the original Bell patent 
(No. 174,465, of 1876,) covered the undulating current, for the trans- 
mission of speech. Many efforts have been made by litigants 
to prove that specific telephones have transmitted articulate speech 
by the make and break current, but without success. If this could 
have been proved the assumption is that the courts would have 
sustained the use of such device as not infringing upon the claims 
of the Bell patent. 

Malapterurus. A fish, sometimes called the thunder fish, an 
inhabitant of African rivers, occurring in the Nile and Senegal. It 



368 STANDARD ELECTRICAL DICTIONARY. 

possesses considerable electric power, similar to that of the gym- 
notus and torpedo, although inferior in amount. 




Fig. 237. Malapterurus. 

Man shole. The cistern-like depression in the ground for giving 
access to the ends of tubes in electric conduits. (See Conduit, 
Electric Subway.) 

Marked End or Pole. The north pole or north seeking pole of 
a magnet, so called because it is usually marked with a notch or 
scratch by the maker. The south pole is called the unmarked end. 

Mass. The quantity of matter in a body. The C. G. S. unit of 
mass is the quantity of matter in a gram. While weight varies with 
latitude and other circumstances, mass is invariable. 

The unit of mass is also denned as the quantity of matter which 
in a balance will counterpoise a standard mass, the gram or pound. 
As the gram is intended to be the mass of one cubic centimeter of 
water at3.09° C. (39 F.), the C. G. S. unit of mass is really 1. 000013 
gram. 

As a primary unit its dimensions are indicated by M. 

Mass, Electric. A term for quantity of electricity. The unit 
mass is such a quantity as at unit distance will act with unit force. 

Matter, Electric. The imaginary substance constituting elec- 
tricity ; a conception used purely as a matter of convenience. 

Matter, Radiant. Matter in the ultra-gaseous or so-called 
fourth state. In the gaseous state the molecules of a gas are in 
perpetual kinetic motion, colliding actually or virtually with each 
other, rebounding from such approach, and striking also the walls 
of the containing vessel. But except for these deflections, which 
are of enormous frequency, the paths of the molecules would be 
perfectly straight. 

In the radiant state matter exists in so high a vacuum that col- 
lisions of the molecules rarely occur, and the moleules simply 
beat back and forth in straight lines from side to side of trie con- 
taining vessel. 

A layer of gas in this condition is termed a Crookes' layer, from 
Prof. William Crookes, who discovered and investigated these 
phenomena. 



STANDARD ELECTRICAL DICTIONARY. 369 

Luminous streams of the molecules are produced by electric high 
potential discharges between electrodes. The course of the discharge 
is normal, in general terms, to the surfaces of the electrodes, and 
reaches from one to the other in a curve or straight line, as the 
case may be. 

These luminous streams are deflected by a magnetic field ; if 
brought to a focus can heat refractory material in that focus to a 
full white heat, and can develop phosphorescence. The latter is 
termed electric phosphorescence. A great variety of experiments 
have been devised to illustrate the phenomena of radiant matter. 
The vacuum is generally produced in a hermetically sealed glass 
vessel into which the electrodes are sealed, and which contain the 
phosphorescent substances or other essentials for the experiments. 
The vessels are termed Crookes' Tubes. 

Matteueci's Experiment. An experiment for showing the 
inductive effect of the discharge of a Ley den jar. Two glass plates 
are supported on standards in a vertical position. Flat coils of 
wire are wound or coiled and secured to one surface of each plate. 
One plate has much finer and longer wire than the other. Metal 
handles are connected to the ends of the finer wire coil. The 
plates are placed with their coils facing each other. A Leyden jar 
is discharged through the coarser coil, while the handles are grasped 
by a person. The shock of the discharge is felt by him. 

Matting, Electric Floor. Matting or floor covering underlaid 
with burglar alarm contacts, so arranged as to be closed by anyone 
walking on the matting. The contacts are connected to a burglar 
alarm system. The object is to provide an alarm if a burglar 
enters a house, in case he should enter a door or window without 
sounding the bell. The latter can be done by cutting out the 
window or part of the door instead of opening it. 

Maxwell's Theory of Light. A theorv of light. It is due to 
J. Clerk Maxwell. 

It supposes the phenomena of electric induction to be due to the 
ether, q. v. It supposes the condition of the ether when convey- 
ing light to be the same as if exposed to the induction of rapidly 
alternating currents or discharges (in this case synonymous). It 
therefore is an electro-magnetic effect if the theory is correct. 

An electric stress such as one due to the induction of an electro- 
statically charged body is not a wave-creating element or factor, 
but is a simple stress. But let this stress be stopped and renewed 
and at once it appears as a wave-forming agency. 

This stoppage and renewal represents evidently a discharge 
succeeded by a charge, or if repeated is equivalent to an intermit- 
tent current or an alternating one. 



370 STANDARD ELECTRICAL DICTIONARY. 

Again the electrostatic stress kept constant may by being carried 
through space carry with it a wave, just as a moving projectile 
carries a wave of air in advance of itself. 

Admitting this much the following consequences follow : 

Since in non-conductors the displacement produces a restitution 
force, which varies as the displacement which is requisite or is a 
criterion for the propagation of waves, while in conductors no 
such force is manifested and the electric energy appears as heat, 
it follows that light vibrations are not possible in conductors, 
because electro-magnetic waves do not exist in them when they 
are in circuit, and conductors should be opaque, while the reverse 
is true for non-conductors. (Daniell.) 

This is carried out often enough to make a striking evidence in 
favor of Maxwell's theory. 

The velocity of propagation of an electro-magnetic disturbance 
in a non-conductor should be equal to that of light. This con- 
stant is proved by mathematical considerations, to be approxi- 
mately the same as the ratio of the electrostatic to the electro- 
magnetic unit of intensity or quantity. This ratio is 3 X io 10 
(30,000,000,000), which is almost exactly the velocity of light. 

It also follows from what has been said that if an electrostatic- 
ally charged body were whirled around a galvanometer needle at 
the rate of 3 X io 10 revolutions per second it should affect it like a 
circulating current. This rate of rotation cannot be attained, but 
Rowland has made manifest the effect of a rotating statically 
charged body upon a magnetic needle. 

The above is the merest outline of Maxwell's theory. The full 
development must be studied in his own and succeeding works. 

Mayer's Floating Magnets. An experiment due to Prof. 
Mayer. A number of sewing needles are magnetized and thrust 
into bits of cork, almost all the way through, with their like poles 
projecting. They are floated in a basin of water and take, under 
the effects of attraction and repulsion, when approached by a 
magnet pole, regular geometric positions, marking out the posi- 
tions of angles of polygons. 

Measurements. The determination of the value of quantities ; 
determination of the factor by which the unitary value must be 
multiplied to produce the quantity under examination. Such are 
the measurement of the voltage of a galvanic battery, or of the 
ohms of resistance of a conductor. Electricity has been termed 
the science of measurement. 

Meg or Mega. A prefix, meaning one million times. A meg- 
ohm is one million ohms ; a megerg is one million ergs ; a mega- 
dyne is one million dynes. 



STANDARD ELECTRICAL DICTIONARY. 



371 



Mercury. A metal ; one of the elements; symbol, Hg; atomic 
weight, 200 ; equivalent, 200 or 100 ; valency, 1 and 2. It is a con- 
ductor of electricity. The following data are o° C. (32 F.) 

Relative Resistance, 62.73 

Specific Resistance, 94-32 microhms. 

Resistance of a wire, 

(a) 1 foot long, weighing 1 grain, 18.51 ohms. 

(d) 1 foot long, 1- 1000 inch thick, 572.3 " 

(c) 1 meter long, weighing 1 gram, 12.91 " 

(d) 1 meter long, 1 millimeter thick 1.211 " 

Resistance of a 1 inch cube, 37 

Percentage increase of resistance per degree C. 1. 
20 C. (68° F.), 

Electro-chemical equivalent (Hydrogen — .0105), 



15 microhms. 

8° F. at about 
.072 percent. 

2.10 mgs. 
I.05 " 




Fig. 238. Mayer's Floating Magnets. 

Mercury Cup. A cup of iron, wood or some material that does 
not amalgamate or is unattacked by mercury, which is filled with 
mercury and made an electrode of a circuit. By dipping the other 
terminal of the circuit into the mercury a very good contact is 
obtained. It is well to cover the mercury with alcohol. The 



372 



STANDARD ELECTRICAL DICTIONARY. 



cup may be filled so that the mercury rises in a meniscus or semi- 
globule above its edges. For some purposes this form is useful, as 
for contacts with the end of a swinging wire or pendulum, because 
in such cases the contact can be made without the contact point 
entering the cup. The point swings through the projecting menis- 
cus without touching the edges of the cup. A mercury cup and 
contact constitute a mercury break. 




Fig. 239. Schallenberg's Alternating Current Meter. 

Meridian, Astronomical. The great circle passing through 
the north and south poles of the celestial sphere. It lies in a plane 
with the corresponding geographical or terrestrial meridian. 

Meridian, Geographic. The true north and south mericlian ; 
the approximate great circle formed by the intersection of a plane 



STANDARD ELECTRICAL DICTIONARY. 373 

passing through north and south poles of the earth with the earth's 
surface. 

Meter, Alternating Current. A meter for measuring alternat- 
ing current, as supplied to consumers, from an alternating current 
system. Like most commercial meters its only function is the 
measurement of quantity ; the potential difference is maintained 
at a constant figure by the generating plant. 

The cut shows the Schallenberg meter. It is simply an alternat- 
ing current motor (see Motor, Alternating Current), with air 
vanes mounted on its spindle. A main coil passes all the current. 
Within this is a second coil complete in itself, and not touching or 
connecting with the other. The latter is built up of copper rings. 
Within the two coils, and concentric with both is a disc of copper 
carried by a vertical spindle. The same spindle carries air vanes, 
and is free to rotate. As it does so it moves the indicating 
machinery. 

The current in the outer coil induces one in the inner coil. Owing 
to lag, the current in the inner one differs in phase from that in 
the outer one, and a rotatory field is produced. The copper disc 
acquires induced polarity, and rotates with speed which normally 
would be in proportion to the square of the current. But the 
object of the meter is to register the current only. The air 
vanes effect this. The resistance of the air to their motion causes 
the rate of rotation to vary directly as the current. 

Meter Bridge. A form of Wheatstone's bridge in which one 
lateral pair of arms is represented by a straight wire. The other 
pair comprise a known resistance, and the resistance to be deter- 
mined. The galvanometer is connected on one side between the 
known and unknown resistance. On the other side its connection 
is moved back and forth along the straight wire until the balance 
is secured and the galvanometer reads zero. 

The relative lengths of wire intercepted between the two ends 
thereof and the movable galvanometer connection are proportional 
to the resistance of these parts and give the necessary data with the 
one known resistance for determining the unknown resistance. 

In the original meter bridge the wire was one meter long, whence 
its name, and was stretched straight. In more recent examples 
the wire varies in length and in one form is bent into a circle or 
spiral, so as to make the instrument more compact. 

The contact is not a sliding one, but is adjusted by trial. The 
contact piece is slid along, but not touching the wire, and from time 



374 



STANDARD ELECTRICAL DICTIONARY. 



to time is pressed down against the wire. This prevents wear of 
the wire. The wire may be made of platinum or of platinum- 
iridium alloy. The latter is very hard and not easily worn out. 

Sometimes, as shown in the cut, three parallel wires are stretched 
along the base-board of the instrument, and arranged so that a 
single wire, two wires or three wires in series can be used for the 
proportional sides of the bridge, thus making it a two-meter or 
three-meter bridge as desired. On the other hand some are made 
of restricted length, as a half or quarter meter only. 




Meter Bridge. 



In the cut/ K is the wire, traversed by the contact key. By 
moving the contact C back and forth in the slot it can be brought 
over any of the three divisions of the wire. H is the handle for 
depressing the key. S is a flat spring, carrying the contact piece 
and holding it up from the wires> except when pressed downwards. 
As shown in the cut, it is in use for calibrating a voltmeter V, 
by Poggendorf 's method, G being the galvanometer and r 1 and r 2 
being resistances. 

Synonyms — Slide Bridge — Slide Balance. 

Meter Candle. A unit of illuminating power ; the light given 
by one standard candle at a distance of one meter. The ordinary 
units of illuminating power are altogether relative ; this one is 
definite. 



STANDARD ELECTRICAL DICTIONARY. 375 

Meter, Chemical Electric. A current meter in which the cur- 
rent is determined by the amount of chemical decomposition which 
it can effect. In the Edison meter the solution is one of zinc sul- 
phate. Two electrodes of zinc are immersed in it, and a fractional 
part of the current is passed through it. The gain in weight of one 
electrode and the loss in the other are proportional to the current. 
Both electrodes are weighed periodically, one acting as check upon 
the other. 

Meter, Current. An instrument for measuring the quantity of 
electricity in current form supplied to consumers. It may be of 
various types. The general principle involved is that in commer- 
cial installations for incandescent light and power supply a fixed 
potential is usually maintained, the multiple arc system being em- 
ployed. Hence all that is requisite is to measure the coulombs 
or the ampere-hours to know what quantity of energy has been 
supplied. 

Meter, Electro=magnetic. A current meter in which the cur- 
rent is measured by its electro-inagnetic effects. 

Meter=millimeter. A unit of resistance. (See Resistance, 
Meter -millim eter . ) 

Meter, Thermal Electric. A current meter in which the cur- 
rent is measured by the heat it imparts to a conductor. In one 
meter a very light helix of mica is poised horizontally over a con- 
ductor, and the whole is enclosed in a case. As the wire is heated 
it causes an ascending current of air which rotates the vane, and 
the latter moves delicate clockwork which moves indicating hands. 
The hotter the wire the more rapidly the air ascends, and conse- 
quently the speed of the vane is proportional to the current, because 
the heat of the conductor is proportional thereto. 

Meter, Time Electric. An electric meter which measures the 
length of time during which current is used. It assumes a con- 
stant current and potential. It is virtually a clock, which is 
turned on when the current passes, and is turned off with the 
current. 

Meter, Watt. A combined current and potential meter. It is 
constructed on the general lines of a Siemens' Electro Dynamom- 
eter. If in it one coil is made of coarse wire and is placed in 
series with the current conductor, and if the other is wound with 
fine wire and is connected as a shunt from point to point whose 
potential difference is to be determined, the instrument becomes a 
watt meter. 

Synonym — Energy Meter. 



376 



STANDARD ELECTRICAL DICTIONARY. 



Methven Standard or Screen. A standard of illuminating power. 
It is the light, emitted by a three-inch Argand gas flame through a 
rectangular aperture in a silver plate car- 
ried by a screen. The aperture is of such 
size and so far distant from the flame as 
to permit the passage of exactly two can- 
dles illuminating power. 

Mho. A unit of conductance, not in 
very general use. It is the reciprocal of 
the ohm. Thus a resistance of ten ohms 
is a conductance of one-tenth mho. 

Mica. A natural mineral, a silicate of 
several oxides ; muscovite. It is used as 
an insulator and dielectric. Its resist- 
ance per centimeter cube after several 
minutes electrification at 20 C. (68° F.) 
is 84 X io 12 ohms (Ayrton). Its specific 
inductive capacity is 5 , air being taken at I, 

Mica, Moulded. An insulating mate- 
rial, whose body is made of mica pulver- 
ized and cemented together with heat and 
pressure and some suitable cement. Shel- 
lac is often used as the cement. 

Micro. A prefix meaning * ' one-mill- 
ionth of;" a micro-farad is one -millionth 
of a farad- 
Micrometer. An instrument for measuring small distances or 
small differences. It generally is based upon an accurate screw 
which may have a worm wheel for head, actuated by a worm or 
helix with graduated head, so that exceedingly small advances of 
the screw may be produced. The pitch of the screw being known 
its actual advance is known. 

Micrometer, Arc. A micrometer for measuring the distance 
between voltaic arc electrodes. 

Micron. A unit of length. It is one-millionth of a meter or 
four one-hundred-thousandths of an inch. 

Microphone. An apparatus which includes a contact of variable 
resistance ; such resistance can be varied in amount by slight vibra- 
tions, such as those produced by sound waves. The apparatus in 
use forms part of a circuit including a telephone and current gener- 
ator. As the contact is varied the resistance of the circuit and 
consequently the current intensity changes and sounds are emitted 




Fig. 241. 
Methven Screen 



STANDARD ELECTRICAL DICTIONARY. 377 

by the telephone corresponding to such changes. If the microphone 
is spoken to, the telephone will emit corresponding sounds, repro- 
ducing the voice. 

It has been found in practice that carbon gives the best micro- 
phone contact. One of the simplest and earliest forms is shown in 
the cut. A short rod or pencil of carbon, A, such as used in 
batteries, is sharpened at the ends and rests loosely in a vertical 
position between two blocks of carbon, C C> in each of which a 
hole is drilled to receive one of the points. The blocks are carried 
on a standard and base D. The blocks are connected with two ter- 
minals X, y, of a circuit, including a telephone and battery. There 
are two contacts to be disturbed. 

If delicately adjusted a fly walking over the base-board will dis- 
turb the contacts enough to produce sounds in the telephone. These 
sounds are possibly not due only to sound waves, but in part to 
absolute mechanical disturbances. 

The various forms of telephone transmitter are generally micro- 
phones. 




Fig. 242. Microphone. 

Microphone Relay. A combined microphone and telephone. 
A microphone is placed close to the diaphragm of a telephone. 
The slight sound waves emitted by the telephone affect the micro- 
phone and are repeated in its circuit. The microphone circuit 
includes a local battery and telephone. 

Microtasimeter. An apparatus for indicating minute changes 
in temperature or atmospheric moisture. 



378 



STANDARD ELECTRICAL DICTIONARY. 



A button of compressed lampblack is placed in series with a bat- 
tery and galvanometer. A strip of some substance, affected in its 




s sA-W 



Fig. 243. MlCROTASIMETER. 

length either by heat or by moisture, is held pressing against the 
button. A slight change in length of the strip varies the resistance 



STANDARD ELECTRICAL DICTIONARY. 379 

of the button and hence affects the galvanometer. In this way 
exceedingly slight changes in heat or moisture may be indicated. 

For heat indications vulcanite may be used. The heat of the 
hand held near it is enough to affect the galvanometer. For mois- 
ture a slip of gelatine is used. The moisture of a damp slip of paper 
two or three inches distant is sufficient to affect the galvanometer. 
In the cut, Fig. 2, shows the general distribution of the apparatus 
in circuit with a battery and galvanometer. C is the base of the 
apparatus, from which the standard, B, with adjusting screw, //, 
rises. The strip of vulcanite is held between I and G. Within D 
is the carbon button (.Fin Fig. 3) pressed between G and E ; A is 
a standard to carry the parts last described. In Fig. 1 it is shown 
as part of a Wheatstone bridge, a, b and c being resistance coils ; 
/ the tasimeter, and g the galvanometer. If a balance is secured, 
any variation in the resistance of the tasimeter will disturb the 
galvanometer. 
Synonym — Tasimeter. 

Mil. A unit of length ; one-thousandth part of a lineal inch. 
It is equal to .025399 millimeter ; 
.000083 f°°t ; 
.001000 inch. 
Mil, Circular. A unit of area; employed in designating the 
cross-sectional area of wires and other circular conductors. 
It is equal to .78540 square mil ; 

.000507 square millimeter ; 
78 X io- s (.00000078) square inch. 
If the diameter of a wire is given in mils, the square of its 
diameter gives its cross-sectional area in circular mils. 

Mil=foot. A unit of resistance. (See Resistance, Mil-foot, Unit of). 
Mil, Square. A unit of area ; one-millionth of a square inch. 
It is equal to .000645 square millimeter ; 
1.2733 circular mil ; 
.000001 square inch. 
Milli. A prefix ; one-thousandth. Thus a milligram is one- 
thousandth of a gram ; a millimeter is one thousandth of a meter. 

Milligram. A unit of weight ; one-thousandth of a gram, q. v. 
It is equal to .015432 grain ; 

.000032 troy ounce. 
Millimeter. A unit of length ; one-thousandth of a meter. 
It is equal to 39.37079 mils ; 
.03937 inch ; 
.00109 yard. 



380 STANDARD ELECTRICAL DICTIONARY. 

Milli=oerstedt. A proposed but not adopted unit of current; 
one-thousandth of an oerstedt. It is equal to one-thousandth of an 
ampere. 

mm. Contraction for millimeters. 

Molar. Referring to phenomena of mass as gravitation. 
Mechanics generally treats of molar laws and phenomena. 

Molar Attraction. The attraction of mass for mass ; gravitation. 
Synonyms — Mass Attraction — Gravitation. 

Molecular Affinity. The attraction of molecules for each other 
as seen in the formation of double salts, the combining of water 
of crystallization with a salt, and in other cases ; a phase of 
affinity belonging to chemistry, although outside of true atomic 
attraction. 

Molecular Attraction. The attraction of molecules ; physical 
affinity. Cohesion, the attraction of similar molecules for each 
other, and adhesion, that of dissimilar molecules, are examples. 
This should be distinguished from molecular affinity, a phase of 
chemical force. 

Molecular Bombardment. When a gas contained in a vessel 
is brought to a sufficient state of rarefaction the molecules cease to 
be subject to the laws of diffusion, but move back and forth in 
straight lines from side to side of the vessel. Their courses can 
be affected by electric discharge, which can cause them to all 
impinge upon one of the electrodes, the positive one, producing 
luminous effects. The path, if referred to the negative electrode, 
tends to be normal to its surface, so that the resultant path may«be 
curved, as the stream of molecules go to the positive electrode. 
The fanciful name of molecular bombardment is given to the 
phenomenon, the luminous effect being attributed to the imping- 
ing of the molecules against the positive electrode as they are pro- 
jected from the negative. The course of the molecules is comparable 
to the stream of carbon particles from the positive to the negative 
electrode in an arc lamp. (See Matter, Radiant.) 

Molecular Chain. The theoretical rows of molecules supposed 
to extend from anode to cathode in an electrolytic cell (see Cell, 
Electric — Grotkuss' Hypothesis) are called molecular chains, i 

Molecular Rigidity. The tendency of the molecules of a mass 
to retain their position in a mass in resistance to polarizing or 
depolarizing force, the first being the effect of a magnetic field. It 
is the theoretical cause of coercive force, q. v., and of residual 
magnetism. (See Magnetism, Residual.) 

Molecule. The smallest particle of matter that can exist alone. 



STANDARD ELECTRICAL DICTIONARY. 381 

It is made up of atoms, but an atom can never exist alone, but only, 
with one or two possible exceptions, combined with one or more 
other atoms as a molecule. The molecules under present condi- 
tions are not in constant contact with each other, but are perpetu- 
ally vibrating through paths, in solids probably in denned paths, in 
liquids and gases in perpetually new paths. The molecules collide 
with each other and rebound. This motion is the kinetic motion 
termed heat. At the absolute zero — 273. 72 C. ( — 460.7 F.) the 
molecules would be in contact and quiescent. In the gaseous 
state the molecules of most substances occupy the same volume ; 
those of a few elements occupy one-half and of others twice the 
normal volume. The mean free path of the molecule of hydrogen 
is about 1-20,000 mm. (1-508,000 inch) (Maxwell) or twice this 
length (Crookes), the collisions in Irydrogen are about 17,750 
millions per second ; the diameter is about 8-10,000,000 mm. 
(8-254,000,000 inch) ; A particle of matter 1-4,000 mm. (1-102,000 
inch) contains, it is supposed, about4o,ooo molecules. The results 
of different authorities vary so widely as to deprive the subject of 
much of its interest. A Sprengel pump, such as used for exhaust- 
ing Geissler tubes, or incandescent lamp bulbs, may leave only one 
hundred-millionth (1-100,000,000,) of an atmosphere present, giving 
the molecules a capability of an average free path of vibration 33 
feet long. 

Moment. When a force is applied so as to tend to produce rota- 
tion around a point, the product of the force by the shortest distance 
from the point of rotation to the extension of the line of the force. 
Such distance is the perpendicular to the extension of the line 
through the point of rotation. 

Mordey Effect. A phenomenon observed in dynamo armatures. 
At full loads the hysteresis decreases. The effect is thus expressed 
by S. P. Thompson. "When an armature core is rotated in a 
strong magnetic field, the magnetization of the iron is being con- 
tinually carried through a cycle, but in a manner quite different 
from that in which it is carried when the magnetizing force is 
periodically reversed, as in the core of a transformer. Mordey has 
found the losses by hysteresis to be somewhat smaller in the former 
case than in the latter." 

Morse Receiver. The receiving instrument formerly universally 
used in the Morse system. It is now but little employed, the 
sounder having displaced it. Several types were invented. 

It consists of machinery wmich carries a reel of paper ribbon 
arranged to be fed over a roller by clockwork. A pencil, inking 
roller, or embossing stylus (for the latter the roller must have a 
groove) is carried by an arm with restricted range of vibration just 
over the paper and roller. The armature of an electro-magnet is 



3 82 



STANDARD ELECTRICAL DICTIONARY. 



attached to the arm. When the magnet is excited the armature is 
attracted and the marking device is pressed on the paper. If the 
clockwork is in operation the marker will make a line as long as 
the armature is attracted. When released no mark will be pro- 
duced. In this way the dots and dashes of the Morse code are 
made on a ribbon of paper. 

As an inking arrangement a small roller is carried by the end 
of the vibrating arm. The embosser, or dry point stylus, was very 
extensively used. The clockwork was generally driven by descend- 
ing weights. 

Synonym — Morse Recorder. 

Mortar, Electric. An electric toy which may have various 
modifications. In the cut a wooden mortar 
with recess to receive a ball is shown. Two 
wires enter the base but do not touch. On 
placing the ball in position and passing a 
spark from a Ley den jar across the interval 
between the wires, the heat and disturbance 
are enough to project the ball. Gunpowder 
may be used, the discharge being passed 
through a wet string to prolong the spark. 




Fig-. 244. Electric 
Mortar. 



Motor, Compound or Compound Wound. 

A motor which has two windings on the field- 
magnets, one in parallel with that on the 

armature, the other in series therewith, exactly as in a compound 

dynamo. (See Dynamo , Compound.) 

Motor, Differential. A differentially wound motor ; with a 
compound wound field, whose series coil and shunt coil are wound 
in opposition to each other. It is virtually a compound wound 
dynamo. (See Dynamo, Compound Wound.) 

Motor, Electric. A machine or apparatus for converting elec- 
tric energy into mechanical kinetic energy. The electric energy 
is generally of the dynamic or current type, that is to say, of com- 
paratively low potential 'and continuous or virtually continuous 
flow. Some electrostatic motors have, however, been made, and 
an influence machine can often be operated as a static motor. 

Electric motors of the current type may be divided into two 
classes— direct current and alternating current motors. 

Direct current motors are generally based on the same lines of 
construction as dynamos. One of the great discoveries in modern 
electricity was that if a current is passed through a dynamo, the 
armature will rotate. This fact constitutes the principle of the 
reversibility of the dynamo. 



STANDARD ELECTRICAL DICTIONARY. 3S3 

Motors built on the dynamo model may be series wound, shunt 
wound, or compound wound, or of the magneto type, in the latter 
case having a fixed field irrespective of any current sent through 
them. The field may be produced by an electro-magnet separately 
excited and unaffected b3 T the current sent through the motor. 

A current passed through a magneto or motor with separately 
excited field will turn it in the direction opposite to that required 
to produce the same current from it were it worked as a generator. 

A current passed through a series wound motor acts exactly as 
above. 

Both these facts follow from Lenz's law, q. v. 

A current passed through a shunt wound motor acts oppositely 
to the above. The direction of rotation is the same as that required 
to produce a current of the same direction. This is because the 
field being in parallel with the armature the motor current goes 
through the magnet coils in the direction the reverse of that of the 
current produced in the armature when it is used as a dynamo. 
Hence this also carries out Lenz's law. 

The compound wound motor acts one way or the other accord- 
ing as its shunt or series winding preponderates. The two may 
exactly balance each other, when there will be no motion at all. 
The series connections of a compound wound dynamo should 
therefore be reversed, making both series and shunt work in unison, 
if the dynamo is to be used as a motor. 

The general principles of the electric motor of the dynamo, or 
continuous rotation type, can only be outlined here. The current 
passing through the field magnets polarizes them and creates a 
field. Entering the armature by the brushes and commutators it 
polarizes its core, but in such a way that the north pole is away 
from the south pole of the field magnet, and the same for the south 
pole. Hence the armature rotates. As it does this the brushes 
connect with other commutator sections, and the poles of the 
armature are shifted back. This action continues indefinitely. 

Another class of motors is of the reciprocating type. These are 
now very little used. (See Motor \ Reciprocating.) 

One valuable feature of continuous rotation electric motors is the 
fact that they absorb energy, to a great extent proportional in 
amount to the work they have to do. The rotation of the armature 
in the field of the motor involves the cutting of lines of force by its 
coils. This generates an electro-motive force contrary in direction 
to that producing the actuating current. The more rapid the rota- 
tion the greater is this counter-electro-motive force. The motor 
armature naturally revolves faster with diminished resistance to 
the motion of the armature. This increases the counter-electro- 
motive force, so that less energy is absorbed. When the motor is 



384 STANDARD ELECTRICAL DICTIONARY. 

called on to do work, the armature rotates more slowly, and the 
counter-electro-rnotive force diminishes, so that the machine absorbs 
more energy. (See Jacobins Law,) 

Motor Electro=motive Force. The counter-electro-motive 
force of a motor. (F. J. Sprague.) 

A motor rotates in virtue of the pull of the field magnet upon the 
poles of the core of its armature. In responding to this pull the 
windings of the armature cuts lines of force and hence generates 
a counter-electro-motive force, for which the above term was sug- 
gested. 

Motor=Generator. A combined motor and generator used to 
lower the potential difference in a portion of a circuit, e. g. , that 
part within a building. 

A motor-generator is a dynamo whose armature carries two com- 
mutators, with two separate windings, one of fine wire of many 
turns, the other of coarse wire of few turns. If the potential of the 
system is to be lowered, the main current is passed through the 
fine winding. This causes the armature to turn motor-fashion, and 
a potential difference is generated by the rotation of the large coils 
in the field. This potential difference is comparatively low and by 
properly proportioning the windings may be lowered to as great a 
degree as required. 

The same apparatus may be inverted so as to raise potential 
difference. It acts for continuous current systems as the induction 
coil transformer does for alternating current systems.. 

Synonym — Continuous Current Transformer. 

Motor, Multiphase, A motor driven by multiphase currents. 
It is arranged in general terms for distribution of the multiphase 
currrents in coils symmetrically arranged around the circle of the 
field. These coils are wound on cores of soft iron. A rotating 
field is thus produced, and a permanent magnet or a polarized 
armature pivoted in such a field will rotate with the field, its poles 
following the poles of the rotatory field. 

The cut, Fig. 245, illustrates the principles of action of a four 
phase current motor, connected to a four phase current dynamo or 
generator. The generator is shown on the left hand of the cut 
and the motor on the right hand. In the generator the armature 
N S is supposed to be turned by power in the direction shown by 
the arrow. Each one of the pair of coils is wound in the reverse 
sense of the one opposite to it, and the two are connected in series 
with each other, and with a corresponding pair in the motor. The 
connection can be readily traced by the letters A A', a a f for one 
set of coils and B B f b b f for the other set. 

For each rotation of the armature two currents, each in opposite 



STANDARD ELECTRICAL DICTIONARY. 



385 



direction, are produced in A A ; , and the same is the case for BB'. 
These currents which have an absolutely constant relation of 
phase, and which it will be seen alternate four times for each rota- 
tion of the armature, regulate the polarity of the field of the motor. 




Four-phase Current Generator and Motor. 



The resultant of their action is to keep the poles of the field magnet 
of the motor constantly traveling around its circle. Hence the 
armature N S of the motor, seen on the right hand of the cut, 
tends to travel around also its north and south poles, following the 
south and north poles of the rotatory field respectively. 

It is not essential that the armature should be a magnet or polarized. 
Any mass of soft iron will by induction be polarized and will be 
rotated, although not necessarily synchronously, with the rotatory 
field. Any mass of copper, such as a disc or cylinder, will have Fou- 
cault currents induced in it and will also rotate. The only compo- 
nents of such currents which are useful in driving the motor are 
those which are at right angles to the lines of force and to the 
direction of motion. A very good type of armature based on these 
considerations is a core of soft iron wound with insulated copper wire 
in one or more closed coils, and so w r oundas to develop the currents 
of proper direction. 

Such an armature is used in the Tesla alternating current motor. 
An efficiency of 85 per cent, has been attained with some of the 
Tesla motors. 

Motor, Prime. A machine used for producing mechanical 
motion against resistance. It may operate by converting heat or 
any other form of kinetic or potential energy into mechanical 
energy of the moving type. A steam-engine and a water-wheel 
are examples of prime motors. 

Motor, Reciprocating. The early type of motor depending 
upon reciprocating motion, such as the motion of a coil in a solen- 



386 STANDARD ELECTRICAL DICTIONARY. 

oid. These were based upon the lines of a steam engine, and have 
been abandoned except for special purposes where reciprocating 
motion is especially required, as in the case of rock drills. 




Fig. 246. Ricordon's Reciprocating Motor. 

In the cut, B is an electro-magnet ; A is an armature ; E a pole 
piece. The current enters by the springs, b b, and by commuta- 
tion is supplied and cut off alternately, thus maintaining a recipro- 
cating movement of the armature and rotation of the fly-wheel. 

Synonym — Pulsating Motor. 

Motor, Series. A motor whose winding on the armature is in 
series with the winding on the field. It is similar to a series 
dynamo. (See Dynamo, Series.) 

Motor, Shunt. A motor whose winding on the armature is in 
parallel with the winding on the field magnets. It is similar to a 
shunt wound dynamo. (See Dynamo, Shunt.) 




Fig-. 247. Multiple Arc Connection. 

Multiple. A term expressing connection of electric apparatus 
such as battery couples, or lamps in parallel with each other. In 



STANDARD ELECTRICAL DICTIONARY. 



387 



the ordinary incandescent lamp circuits the lamps are connected 
in multiple. 
Synonym— Multiple Arc. 

Multiple Arc Box. A resistance box arranged so that the coils 
may be plugged in multiple instead of in series. Such can be used 
as a rheostat, as the resistance can be very gradually changed by 
putting the coils one by one into parallel with each other. Thus 
by adding in parallel with a 10 ohm coil a 10,000 ohm coil the 
resistance is decreased to 9.999001 ohms, and thus the resistance 
can be very slowly changed without sudden stops or abrupt changes. 

Multiple Series. Arrangements of electric apparatus in a circuit 
in a number of series, which minor series are then arranged in 
parallel. The term may be used as a noun, as " arranged in mul- 
tiple-series," or as an adjective, as " a multiple-series circuit." 



< M) 




Fig-. 248. Multiple Series Connection. 

Multiple Switch Board. A switch board on whose face con- 
necting spring jacks or other devices are repeated for the same 
circuits, so that different operators have each the entire set of con- 
nections repeated on the section of the board immediately in front 
of and within their reach. This multiplication of the same set 
of connections, giving one complete set to each operator, gives 
the title "multiple" to the type of switch board in question. 
The typical multiple switch board used in telephone exchanges 
is the best example of this construction. The calling annun- 
ciators of the subscribers are distributed along the bottom of 
the board extending its full length. To each operator a given 
number is assigned, all within reach of the right or left hand. This 
gives five or six feet length of board to each, and an operator only 
responds to those subscribers within his range. But any one of his 
subscribers may want to connect with any of the others in the 
entire central station. Accordingly in front of each operator 
spring jacks are arranged, one for each of the entire set of sub- 
scribers connected in that office. The operator connects as required 
any of the calling subscribers, who are comparatively few, to any 
one of the large number served by the central station. Thus the 
entire set of subscribers' spring jacks are multiplied over and over 
again so as to give one set to each operator. 



388 STANDARD ELECTRICAL DICTIONARY. 

Multiple Wire Method for Working Electro= magnets. A 

method for suppressing sparking in working electro-magnets inter- 
mittently. The magnet core is wound with a number (from four 
to twenty) of separate layers of fine wire. A separate wire is taken 
for each layer and all are wound in the same direction, from one 
end to the other of the space or bobbin without returning. The 
ends are then joined so as to bring all the wires in parallel. The 
effect of this is that as the coils vary in diameter the time con- 
stants of each is different from that of the others, the coefficient of 
self-induction being less, and the resistance being greater for the 
coils farthest from the central axis. Thus the extra currents run 
differently in the different coils, and only a comparatively small 
spark can be produced owing to the division of forces thus brought 
about. 



ftttftf * ?**o * a Q-*. 



SLSUL 




^flLg.P-Q,.ft-ft-0 » g « X^ 
UUUUUL* Q g K> 9 , 9 ft A. 

Fig. 249. Diagram Illustrating Multiple Wire Working. 

Multiplex Telegraphy. Any system of telegraphy transmitting 
more than four messages simultaneously over a single wire. 
Properly it should apply to all transmitting more than one, but 
conventionally has the above restricted meaning, distinguishing it 
from duplex and quadruplex telegraphy. 

Multiplying Power of a Shunt. When a resistance is placed 
in parallel with a galvanometer on a circuit the following relation 
obtains. I*et s and g equal the resistances of the shunt and gal- 
vanometer respectively, S and G the currents in amperes passing 
through them, V the potential difference between their common 
terminals, and A the whole current in amperes. Then we have 
s + g s + g ^ 

A = X G, and is termed the multiplying power of 

s s 

the shunt, as it is the factor by which the current passing through 
the galvanometer must be multiplied by to produce the total 
current. 

Muscular Pile. A species of voltaic battery, often termed Mat- 
teueci's pile, made up of alternate pieces of muscle cut longitudi- 
nally and transversely respectively. The different pieces represent 
the elements of a battery, and their difference of potential is 
naturally possessed by the pieces. 

Myria. A prefix ; one million times. Thus myriavolt means 
one million volts. 



STANDARD ELECTRICAL DICTIONARY. 389 

N. (a) Symbol for north pole or north-seeking pole of a magnet. 
(b) Symbol for the number of lines of force in a magnetic circuit. 

Nairne's Electrical Machine. The cylinder electrical machine, 
q. v. 

Napierian Logarithms. A series of logarithms the base of whose 
system is 2.72818. They are also called hyperbolic logarithms. 

Nascent State. An element just separating from a combination 
possesses at that time higher affinities than after separation, and can 
effect more powerful chemical changes. 

It is sometimes attributed to a differential time of existence in 
the atomic modification, before the freed atoms have united to 
form molecules. 

Natural Currents. A term for earth currents. (See Current, 
Earth.) 

Needle, (a) A term applied to a bar magnet poised horizontally 
upon a vertical point, or suspended in a horizontal position by a 
filament. Thus the magnet in a mariner's compass, which maybe 
a substantial bar magnet, is called a magnetic needle. 

(6) An indicator in general shape like the hand of a clock. (See 
Annunciator, Needle — Telegraph, Needle.) 

Needle of Oscillation. The magnetic needle poised horizon- 
tally, and used for measuring the intensity of the earth's magnetic 
field, or of an artifical magnetic field, by the method of oscilla- 
tions. The intensities of the field is inversely as the square of the 
number of oscillations performed in a given time. 

Needle, Telegraphic. The index in needle telegraphy (see 
Telegraph, Needle), whose motions indicate the characters it is 
desired to transmit. 

Negative Charge. One of the two kinds of electric charges. 
The other is the positive. 

By the double fluid hypothesis this is assumed to be a charge of 
a particular kind of electricity — negative electricity. 

By the single fluid hypothesis it is supposed to be caused by the 
absence of part of the normal electricity of a surface. The reverse 
is held by some theorists. 

The subject is so purely theoretical that neither of the two 
nypotheses is accepted as final. 

Negative Electricity. The kind of electricity with which a 
piece of amber is charged by friction with flannel ; resinous elec- 
tricity. (See Electrostatic Series.) 



390 STANDARD ELECTRICAL DICTIONARY. 

In a galvanic battery the surface of the zinc plate is charged with 
negative electricity. 

According to the single fluid theory negative electrification con- 
sists in a deficiency of electricity. 

Negative Element. In a voltaic cell the plate not dissolved by 
the solution ; the one which is positively charged ; the copper, 
platinum, or carbon plate in the usual type of battery. 

The current is assumed to flow from negative element to posi- 
tive element (the zinc plate) through the wire or other external 
conductor. 

Nerve Currents. Currents of electricity obtained from nerves. 
They are much more feeble than those obtained from muscle, but 
are produced in the same general ways. 

Network. Conductors in parallel and crossing each other, with 
connections at the junctions. 

The term is sometimes so loosely applied as to include parallel 
conductors. 

Neutral Line of Commutator. The diameter of a commutator 
which connects its Neutral Points, q. v.; sometimes termed the 
diameter of commutation ; the diameter approximately at right 
angles with the lines of force. The commutator brushes are 
applied at the extremities of this diameter. 

Neutral Point of a Commutator. The points of a commutator 
at which no lines of force are cut ; the points at the extremities of 
a diameter which, except for the lag, would be at right angles to 
the lines of force ; the points at which the brushes touch the com- 
mutator. 

Neutral Point, Thermo=electric. A temperature marking a 
point of no thermo-electric difference of potential. If the junctions 
of a thermo-electric couple are at temperatures, one a little over and 
the other an equal amount under the neutral point, no current will 
be developed. At the neutral point the thermo-electric polarities 
are reversed. Differences of temperature above it give currents of 
reverse direction to those given by corresponding differences 
below it. For an iron-copper couple the neutral point is 274.5 C. 
(526 F.) 

Synonym — Neutral Temperature. 

Neutral Relay Armature. An unpolarizable armature for use 
with a relay; an armature of soft iron or iron wire; as distinguished 
from a polarized armature. 

Neutral Wire. The central wire in the three wire system, q. v., 



STANDARD ELECTRICAL DICTIONARY. 



391 



of electric distribution ; the wire connected to a point between the 
two dynamos, or otherwise to the central point of the current 
generator. 




Fig. 250. Diagram of Three Wire System Showing Neutral Wire. 

Neutral Wire Ampere Meter. An ampere meter connected in 
the circuit of the neutral wire to determine the current passing 
through it. Such determination is for the purpose of ascertaining 
how much more work is being done by one of the lateral leads 
than by the other. 

Synonym — Balance Ampere Meter. 

N. H. P. Symbol or contraction for " nominal horse power. ' ' 
This is a basis for rating the size of an engine. 

Nickel. A metal; one of the elements; atomic weight, 58.8 ; 
equivalent, 29.4 ; valency, 2 ; specific gravity, 8.8. It is a con- 
ductor of electricity. 

Relative resistance, annealed (Silver — 1), 

Specific Resistance, 

Resistance of a wire 

(a) 1 foot long, weighing 1 grain, 

(b) 1 foot long, yoVo i ncn thick, 

(c) 1 meter long, weighing 1 gram, 

(d) 1 meter long, 1 millimeter thick, 
Resistance of a i-inch cube, 
Electro-chemical equivalent, (Hydrogen = .0105) .3087 nigs. 

It is strongly paramagnetic, but loses this quality at 350 C. 
(662 F.) 

It is important as a constituent of German silver, an alloy much 
used for resistance coils. 

Nickel, Bath. A bath for the electro-deposition of nickel. A 
great many formulae have been given. Metallic nickel is dissolved 
in 1 vol. sulphuric acid mixed with 2 vols, water.. Neutralize with 
ammonia, and add of ammonium sulphate one-half the weight of 
metallic nickel originally used ; 135 parts of nickel will be enough 
for a bath of 10,000 parts. 



8.285 
12.47 microhms. 

1.578 ohms. 

74.03 " 
1.060 " 
,1587 " 
4.907 microhms. 



4 parts, 


3 


(< 


IOO 


<i 


i 


(< 


i 


<< 


20 


it 



392 STANDARD ELECTRICAL DICTIONARY. 

Other formulae are as follows : 

Double nickel-ammonium sulphate, 

Ammonium carbonate, 

Water, 

Nickel sulphate, nitrate or chloride, 

Sodium bisulphate, 

Water, 

Nickel anodes are used in the bath to maintain the strength. Too 
much care cannot be exercised in the absolute cleanliness of the 
articles to be plated. A too akaline bath gives a disagreeable yellow 
color to the deposit ; too acid a bath gives badly adhering deposits. 

Night Bell. An alarm bell in a telegraph office, which bell is 
connected at night to give a loud signal to attract the operator's 
attention. It is used in telephone exchanges and is connected so 
as to ring as long as a subscriber remains unanswered after calling. 

Nobili's Rings. When a dilute solution of copper acetate is 
placed on a bright silver plate and a strip of zinc is touched to the 
silver beneath the copper, a series of rings of copper are formed by 
electrolysis around the zinc. These are Nobili's rings. 

If for the copper acetate a solution of lead oxide in potassium 
hydrate solution is substituted, and if the polished plate which 
may be German silver is connected to the positive electrode of a 
battery, and a platinum wire connected to the negative pole is 
immersed in the liquid, it determines the formation of beautiful 
iridescent rings of lead binoxide. The platinum wire is sometimes 
sealed in glass so that only its point projects. 

The colors are due to interference of light, the layers of lead oxide 
being extremely thin. 

The lead binoxide is formed by secondary reaction. Metallic 
lead is first deposited on the negative pole. The oxygen which 
goes to the positive pole formed by the polished plate produces 
lead binoxide which is deposited there in rings. The reaction is 
comparable to that of a storage battery. 

Synonyms — Metallochromes — Electric Rings. 

Nodular Deposit. A deposit obtained in electroplating, charac- 
terized by irregular thickness ; due to too low density of current. 

Non=conductor. A material that does not conduct electricity 
except with great difficulty ; a substance of very high resistance. 
Synonym — Insulator — Dielectric. 

North Pole, (a) The north-seeking pole of a magnet ; the pole 
of a magnet which tends to point to the north, and whence lines of 



STANDARD ELECTRICAL DICTIONARY. 



393 



force are assumed to issue on their course to the other pole of the 
magnet. 

(b) The North Pole of the earth. Treating the earth as a magnet, 
and accepting the above nomenclature the north pole should be 
termed the south pole. (See Austral Pole — Boreal Pole.) 

North=seeking Pole. The pole of a magnet which tends to 
point to the north ; the north pole of a magnet. 

Null Method. Any method of obtaining measurements or com- 
parisons, in which the measurement is correct when the deflection 
of the galvanometer or other indicator is zero, nought or null. The 
Wheatstone Bridge (see Bridge, Wheatstone) is an example of a 
null method. 

Two obvious advantages attach to null methods in electric gal- 
vanometer work. One is that an uncalibrated galvanometer can be 
employed. The other is that a galvanometer of any high degree of 
sensitiveness can be employed, there being no restriction as to its 
fineness of winding or highness of resistance. 

£1. (Greek capital " Omega " or O) symbol for megohm. 
go. (Greek omega or o) symbol for ohm. 




Fig. 251. Oerstedt's Discovery. 

Occlusion. An absorption of gases by metals. Palladium will, 
if used as the hydrogen evolving electrode in decomposing water, 
absorb 980 times its volume of hydrogen, which is said to be 
occluded. The metal may also be heated in hydrogen and allowed 
to cool therein, when occlusion occurs. Platinum will occlude 
4 times its volume of hydrogen; iron, 4.15 times its volume of 
carbon-monoxide ; silver, 7 times its volume of oxygen. Metals 
with occluded gases may serve as elements in a galvanic couple. 
(See Gas Battery.) A metal expands in occluding a gas. 



394 



STANDARD ELECTRICAL DICTIONARY. 



In the storage battery it is believed that occlusion plays a part, 
hydrogen and oxygen being respectively absorbed by the two sets 
of plates, and acting as they do in Groves' gas battery. 

Oerstedt. Name proposed for the unit of current strength, but 
not adopted. The ampere is the accepted name. 

Oerstedt's Discovery. Oerstedt discovered in 1820 that a 
magnetic needle tended to place itself at right angles to a current 
of electricity. This fundamental experiment is the basis of the 
galvanometer. 

Ohm. The practical unit of resistance ; io 9 C. G. S. electro-mag- 
netic units. The legal ohm is the resistance of a mercury column 
1 square millimeter in cross-sectional area and 106 centimeters in 
length. There has been considerable confusion, owing to inac- 
curacy in early determinations, in the valuation of the ohm. In 
this work the legal ohm is used. The different ohms will be found 
defined in their place. Resistance units of various names may 
also be consulted. 

The following table gives the relative values of the different 
ohms. 





Length of 
Mercury 
Column in 
Centi- 
metre. 


True 
Ohm. 


B. A. 
Ohm. 


Board of 
Trade 
Ohm. 


Legal 
Ohm. 


True Ohm, - - - 
B. A. Ohm, - - - 
Board of Trade Ohm, 
Legal Ohm, - - - 


106.24 
IO4.9 
106.3 
I06.O 


I 

.9874 
I.OOO50 

•9977 


I. OI28 
I 

I.OI33 
I.OII2 


•9994 
.9868 
I 
.9971 


I.0022 

.9889 

I.0028 

I 



Ohmage. The Resistance of a circuit expressed in ohms. 

Ohm, B. A. The British Association unit of resistance ; the 
resistance of a column of mercury 1 square millimeter in cross- 
sectional area and 104.9 centimeters long ; the B. A. Unit of 
Resistance. 

Ohm, Board of Trade. The approximate ohm as recommended 
by the British Board of Trade on the advice of a committee (SirW. 
Thomson, Dr. J. Hopkinson, Lord Rayleigh and others). It is the 
resistance of a mercury column one square millimeter in section , 
and 106.3 centimeters long at o° C. (32 F.) 

Synonym — New Ohm. 

Ohmic Resistance. True resistance as distinguished from 
spurious resistance, or counter-electro-motive force. 



STANDARD ELECTRICAL DICTIONARY. 



395 



Ohm, Legal, The practical unit of resistance. The resistance 
of a column of mercury one square millimeter in cross-sectional area 
and 106 centimetres long at o° C. (32 F.) The ohm used previously 
to 1884 is the B. A. Unit of Resistance, q. v. 

One legal ohm = 1.0112 B. A. Units, and 1 B. A. Unit = 0.9889 
legal ohm. 

The resistance of a copper wire 1 foot long and -j-^ inch in 
diameter is about 10 ohms. The resistance of 1 mile of iron wire 
Ys inch in diameter is about 10 ohms. 

Synonym — Congress Ohm. 

Ohmmeter. An instrument for measuring directly the resist- 



S? -f 



Fig. 252. Theory of Ohmmeter. 

ance of a conductor or of any part of a circuit through which a 
strong current is passing. It is the invention of Prof. W. E. 




Fig". 253. Ohmmeter. 
Ayrton. It contains two fixed coils at ri^ht angles to each other 



396 STANDARD ELECTRICAL DICTIONARY. 

acting on the same needle of soft iron. One coil is of thick wire 
and is placed in series with the resistance to be measured. The other 
is of very thin wire and is placed in parallel with the same resistance. 
One wire acts by the total current, the other by the potential differ- 
ence between the ends of the resistance. The action on the soft 
iron needle is due to the ratio of potential difference to total 
currents, or to the resistance itself. By properly designing and 
proportioning the coils the angular deflections of the needle are 
made proportional to the resistance. 

In use the thick wire may be kept permanently in circuit. On 
connecting the binding posts of the thin wire coil to any two parts 
of the circuit its resistance is at once given by the deflection of the 
needle. 

When no current is passing the needle rests in any position. A 
current in the thick coil brings it to zero. A current simultane- 
ously passing through the thin high resistance coil brings about 
the deflection. 

The instrument is a commercial rather than a scientific one. 

Ohm's Law. The fundamental law expressing the relations 
between current electro-motive force and resistance in an active 
electric circuit. It may be expressed thus : 

(a) The current strength is equal to the electro-motive force 
divided b}^ the resistance. 

(b) The electro-motive force is equal to the current strength 
multiplied by the resistance. 

(c) The resistance is equal to the electro-motive force divided 
by the current strength. 

All these are different forms of the same statement. Algebraic- 
ally the law is usually expressed thus, (a) C = E/R. It may also be 
expresed thus : (b) E = C R and (c) R = E/C, in which R denotes 
resistance, C denotes current strength, and E denotes electro-mo- 
tive force. 

Ohm, True. The true ohm is the resistance of a column of 
mercury i square millimeter in cross-sectional area, and 106.24 
centimeters long. (See Okm.) 

Synonym — Rayleigh Ohm. 

Oil Insulation. Oil insulation has received several applications 
in electrical work. It has been proposed for use in underground 
conduits. These it was proposed to fill with oil after the inser- 
tion of the conductors, the latter properly wrapped with cotton or 
other covering. For induction coils it has been very successfully 
used. Its principal utility depends on the fact that it is liquid, so 
that if pierced by a spark it at once closes again. A solid insulator 



STANDARD ELECTRICAL DICTIONARY. 397 

if pierced is permanently injured. It is also used in telegraph 
insulators (see Insulator, Liquid) to prevent surface leakage. 

Olefiant Gas. A compound gas ; C 2 H 4 ; composed of carbon, 
24 ; hydrogen, 4 ; molecular weight, 28 ; specific gravity, .981. 

It is a dielectric of about the resistance of air. Its specific induc- 
tive capacity at atmospheric pressure is 1.000722 (Boltzman.) 

Synonym — Ethene ; heavy carburetted hydrogen. 

Open. adj. An electric circuit is said to be open when it is cut 
or broken so that no current can pass through it. The term may 
be recollected by thinking of a switch ; when open no current can 
pass through it. The same adjective is applied to magnetic circuits, 
an air gap implying an open circuit. 

Open Circuit Oscillation. An oscillation of current in open 
circuit so that a spark discharge accompanies it. It is produced by 
electric resonance in a simple circle or loop of wire with ends 
placed near together but not touching, if the circuit is of such size 
that its period of oscillation corresponds with that of the inducing 
discharge. (See Resonance, Electric.) Its period depends entirely 
on the self-induction of the circuit. 

Ordinate. In a system of plane co-ordinates (see Co-ordinates), 
the distance of any point from the axis of abscissas measured 
parallel to the axis of ordinates. 

Ordinates, Axis of. The vertical axis in a system of co-ordi- 
nates, q. v. ' 
Synonym — Axis of Y. 

Organ, Electric. An organ in which the air blast is admitted 
or excluded from the different pipes by electric mechanism. 

The outlines of the system are a series of contacts worked by the 
keys and stops, which cause, when operated by the organist, a cur- 
rent to pass through electro-magnets, opening the valves of the 
different pipes. Thus the manual may be at any distance from 
the organ, and a number of organs may be worked upon the same 
manual. As many as five in a single cathedral are thus connected 
to a manual in the chancel. 

Orientation of a Magnetic Needle. The acquirement by a 
magnetic needle of its position of rest, with its magnetic axis in 
the magnetic meridian. 

Origin of Coordinates. In a system of linear co-ordinates the 
point of intersection of the axes ; the point whose co-ordinates are 
both zero. 

Oscillating Needle. A small light bar magnet suspended by a 



398 STANDARD ELECTRICAL DICTIONARY. 

filament and employed in determining the intensity of a magnetic 
field by the oscillations it completes in a given time after a given 
disturbance. 

Oscillations, Electric. In static electricity the sudden and very 
rapid alternations in the discharge of a static condenser. This dis- 
charge of the disruptive order seems a single one, but is really 
composed of a number of discharges alternating in direction and 
producing electro-magnetic ether waves, probably identical with 
light waves except that they are longer and far less rapid. 

Oscillatory Electro=motive Force. Electro-motive force rap- 
idly changing in sense or in direction, so that it presents an oscil- 
latory character. The alternating current and the telephone 
current as used in practice are actuated by this type of electro-motive 
force. 

Osmose, Electric. When two liquids are separated by a 
porous diaphragm, and a strong current of electricity is passed 
through from the liquid on one side, through the diaphragm, to 
the liquid on the other side, the liquid on the side towards which 
the current is passing rises in level. The process is termed electric 
osmose. When a liquid is forced through a diaphragm a current 
is produced ; in other words electric osmose is reversible. The 
current thus produced is termed a diaphragm current. 

Oscillation, Electric. The phase of discharge of a static con- 
denser in one direction. It is usually followed by a discharge in 
the opposite direction constituting a second oscillation, and so on, 
so that a great number of exceedingly short oscillations are com- 
prised. Thus, in the discharge of the Leyden jar a large number 
of oscillations of current back and forth are produced, the current 
alternating like the swings of a pendulum. 

These oscillations are supposed to affect the ether, producing 
waves in it identical with light waves, except that we have not 
been able yet to produce them short enough to affect the visual 
organs. The waves thus produced can be reflected or refracted ; 
some substances are transparent for them and others opaque. 
There is a possibility that man may yet succeed in producing elec- 
tric oscillations of sufficient frequency to bring about the direct 
production of light. 

Oscillatory Displacement. Hypothetical displacement currents 
of rapidly alternating direction produced in the oscillatory dis- 
charge of a Leyden jar or static condenser. 

Oscillatory Induction. Induction produced by sympathetic 
action of an oscillatory discharge or by electric resonance. (See 
Oscillations^ Electric — Resonance^ Electric — Resonator , Electric.) 



STANDARD ELECTRICAL DICTIONARY. 399 

Outlet. The part of an electrolier or electric light fixture out 
of which the wires are led for attachment of an incandescent light 
socket. 

Output. The rate of energy delivered or of work done by a 
machine. In the case of a current generator it is the volt-coulombs 
per given second, or better the volt-amperes delivered at its outer 
circuit terminals. 

Output, Magnetic. The analogue in a magnetic circuit of the 
output of an electric circuit. It is the product of the magnetizing 
force by the induced magnetism. 

Output, Unit of. As a unit of output of a dynamo Prof. Syl- 
vanus P. Thompson has proposed 1,000 watts, or one kilowatt. 
This unit is now frequently used. To completely define the 
dynamo, however, the amperage or the voltage must also be given, 
as a 10 kilowatt — no volt machine, or a 10 kilowatt — 99 ampere 
machine. 

Over=Compounding. A proportioning of the series and shunt 
windings of a compound dynamo, so that the voltage of the ter- 
minals rises with the load or output enough to allow for the drop in 
mains, thus maintaining the potential for full load at distant points 
in a district. It is carried out by an increase of ampere-turns in 
the series winding. 

Overload. In an electric motor a mechanical load put upon it so 
great as to prevent economical working. One effect of such a load 
is to make the armature run so slowly as to unduly reduce the 
counter-electro-motive force and hence to permit so much current 
to pass through the coils as to heat them, perhaps injuriously. In 
this case the production of heat implies the waste of energy. 

Overtype Dynamo or Motor. A dynamo or motor whose arma- 
ture is placed above or in the upper part of the field magnets, the 
yoke piece of the magnets being in or resting upon the base of the 
machine. 

Ozone. An alio tropic form of oxygen. It possesses much more 
energetic chemical properties than oxygen. It is supposed to con- 

O 
tain three atoms of oxygen in its molecule, represented thus: /\ 

O— -O 

It is produced by electric discharges and it is its peculiar odor 
which is noticed about an electric machine, and sometimes in a 
thunder storm near the path of a lightning flash. 

In the electrolysis of water some ozone may be produced, thus 
diminishing the volume of the oxygen or of the mixed gases given 
off. This is a source of inaccuracy in a gas voltameter; 



400 STANDARD ELECTRICAL DICTIONARY. 

Pacinotti's Inductor. The Pacinotti or Gramme Ring. (See 
Pacinotti's Ring.) 

Pacinotti's Ring. A ring of iron wire wound with coils of 
insulated wire at right angles to its circular axis, and used as the 
armature of a dynamo or motor. A number of connections are 
taken from the coils to a central commutator. 

Fio. 6. 




Fig. 254. Pacinotti's Machine, with Ring Armature. 

If such a ring with its coils is rotated in a field, current can be 
taken from points of the commutator on a line at right angles to 
the lines of force entering the ring. 

The ring was discovered in 1862 by Pacinotti, and later was inde- 
pendently discovered by Gramme. It is often known as the 
Gramme ring. 

Pacinotti Teeth. Projections on a cylindrical or drum arma- 
ture, between which in the grooves formed thereby, the wire is 
wound. The teeth being of iron tend to diminish the reluctance or 
magnetic resistance of the interpolar space, or interval between 
the poles of the field magnet. 

Synonym — Pacinotti Projections. 

Paillard Alloys. Non-magnetic palladium alloys, invented by 
Paillard, of Switzerland, used in anti-magnetic watches. The fol- 
lowing are given as the compositions of several such alloys : 
I. II. 

Palladium, 60 to 75 parts 50 to 75 parts 

Copper, 15 to 25 * * 20 to 30 * ' 

Iron. 1 to 5 " 5 to 20 " 



STANDARD ELECTRICAL DICTIONARY 



401 



The following are more complex : 






I. 


II. 


Palladium , 


65 to 75 parts 


45 to 50 parts 


Copper, 


15 to 25 


15 to 25 " 


Nickel, 


1 to 5 


2 to 5 " 


Silver, 


3 to 10 " 


20 to 25 " 


Gold, 


1 to lyi " 


2 to 5 " 


Platinum, 


^ to 2 


2 to 5 " 


Steel, 


1 to 5 


2 to 5 " 



These alloys are used for balance springs, as well as for the bal- 
ance wheels and escapement parts of watches. The elasticity of 
recently produced springs has been found to be very satisfactory. 

Page Effect, The sounds produced by magnetizing and demag- 
netizing a bar of iron or steel ; the magnetic tick. The sounds are 
strong enough to produce a telephonic effect. (See Magnetic Tick.) 

Palladium. A metal of the platinum series. It has the highest 
power of occlusion, q. v., of all metals. It is the characteristic 
ingredient of non-magnetic watch alloys. 

Palladium used as an electrode in the electrolysis of water will 
occlude 936 volumes of hydrogen, and the hydrogen-palladium 
alloy will exceed in size the original electrode. 




Fig. 255. Luminous Pane. 

Pane, Luminous. A pane of glass, one side of which has pasted 



402 STANDARD ELECTRICAL DICTIONARY. 

to it a long zigzag strip of tinfoil. A design is made by cutting 
through the strip. On discharging a Leyden jar or an electric 
machine through the strip sparks appear where the tinfoil is 
severed, thus producing the design in a luminous effect. Many 
variations can be employed in their construction. 

Pantelegraphy . A system of telegraphy for transmitting designs, 
maps, drawing, and the like by telegraphy. (See Telegraphy, Fac- 
simile.) 

Paper Filaments. Filaments of carbon for incandescent lamps 
made from paper. 

This is one of the earliest materials practically used. The paper 
is cut out of proper shape, and is carbonized in a close vessel, while 
embedded in powdered charcoal or some other form of carbon to 
absolutely cut off access of air. It is then placed in the lamp 
chamber and flashed or subjected to the regular treatment. 

Parabola. A curve ; one of the conic sections. It is approxi- 
mately represented by a small arc of a circle, but if extended 
becomes rapidly deeper than a half circle. 

If, from a point within called the focus, lines are drawn to the 
curve and then other lines are drawn from these points parallel to 
the axis, the angles of incidence will be equal to the angles of 
reflection as referred to tangents at the points where the lines 
touch the curve. 

Parabolic Reflector. A reflector for a light, a paraboloid or 
surface of revolution whose section is a parabola. A light placed 
at its focus has its rays reflected parallel to each other. 

Examples of parabolic reflectors are seen in electric search lights 
and in locomotive head-lights. They are employed in electric 
search lights. The arc light must be of such construction as to 
maintain its ignited points always at the same point, the focus of 
the paraboloid. 

Paraffine. v. To coat or saturate with paraffine wax. Paper 
may be paraffined by dipping in the wax, or by being sprinkled 
with fragments of wax, subsequently melted in with a hot iron or 
otherwise. The tops of battery carbons are often paraffined to 
prevent the acid from rising in the pores by capillary attraction and 
rusting the connections. 

Paraffine Wax. A hydro-carbon composed principally of mixtures 

of the higher members of the paraffine series C n H ? n | 2, It is 
made from cannel coal, coal tar, or petroleum by distillation. It is 
an insulator. Its resistance at 46 C. (114.8 F.) per centimeter 
cube is 34,000 X io 12 ohms, or about the highest resistance known. 



STANDARD ELECTRICAL DICTIONARY. 403 

Its specific inductive capacity (for milky wax) is 2.47 (Schiller). 
For clear wax it is given as follows by different authorities : 

1.92 Ayrton. 

1.96 Wiillner. 

1.977 Gibson & Barclay. 

2.32 Baltzmann. 
It is extensively used in condensers and other electric apparatus 
as a dielectric and insulator. 

Paragreles. Protectors against hail; lightning rods used to 
guard fields against hail ; of little or no real utility. 

Parallax. The apparent change in position of an object when 
looked at from two points of view. By looking at an object a few 
feet distant first with one eye and then with the other, the shifting 
in apparent position is seen. 

In reading the position of an indicator or needle over a scale 
parallax introduces an error unless the eye is held vertically over 
the needle. By making the dial of looking-glass and holding the 
eye so that the reflection of its pupil is bisected by the needle this 
verticallity is ensured. 

Parallel, (a) In the nomenclature of electric circuits two or more 
conductors leading from one point to another, are said to be in 
parallel. 

(b) When two or more conductors connect two main leads of com- 
paratively large size and low resistance they are said to be in 
parallel or in multiple arc. This order is easiest pictured as the 
rungs of a ladder in parallel connecting its two sides representing 
the main leads. 

It may be used as a noun as " arranged in parallel," or as an 
adjective as " a parallel circuit," the opposite of series, q. v. 

Paramagnetic, adj. Possessing paramagnetic properties ; tend- 
ing to occupy a position with the longer axis parallel to the lines 
of force of a magnetic field ; having magnetism ; attracted by a 
magnet. 

' * If a homogeneous isotropic substance is placed in a magnetic 
field it becomes magnetized at every point in the direction of the 
magnetic intensity at that point, and with an intensity of magnet- 
ization proportional to the magnetic intensity. When the positive 
direction of the induced magnetization is the same as that of the 
magnetic intensity the substance is called Magnetic or Paramag- 
netic ; when it is opposite, the substance is called Diamagnetic" 
(Emtage.) 

A paramagnetic substance has high permeability or multiplying 
power for lines of force, hence in a magnetic field a bar of iron, 



404 STANDARD ELECTRICAL DICTIONARY. 

etc., is in unstable equilibrium unless its longer axis is parallel 
with the lines of force in order to reduce as much as possible the 
reluctance of the circuit. 

Iron is the most paramagnetic of all substances. Other para- 
magnetic metals are : Nickel, cobalt, manganese, platinum, cerium, 
osmium, palladium. Diamagnetic metals are bismuth, antimony, 
zinc, tin, mercury, lead, silver, copper, gold, arsenic. Bismuth is 
the most diamagnetic of all metals. 

Of gases oxygen is most paramagnetic. Becquerel calculated that 
a cubic yard of oxygen condensed would act on a magnetic needle 
as powerfully as 5.5 grains of metallic iron. Liquefied oxygen will 
adhere to the poles of a magnet. 

Changes of temperature and of other conditions may affect a 
body's magnetism. Thus hot oxygen is diamagnetic, and a sub- 
stance paramagnetic in a vacuum may be diamagnetic in air. 

Of liquids, solutions of iron or cobalt are paramagnetic ; water, 
blood, milk, alcohol, ether, oil of turpentine and most saline solu- 
tions are diamagnetic. 

Paramagnetism, (a) The science or study of paramagnetic sub- 
stances and phenomena. 

(b) The magnetic property of a paramagnetic substance ; that of 
being attracted by a magnet, and of arranging itself with its longer 
axis parallel with the lines of force of a magnetic field. 

Parchmentizing. If cellulose is treated with a mixture of two 
parts of sulphuric acid and one part of water perfectly cold, it 
becomes like parchment. It should at once be washed with water, 
and then with ammonia and water. The Swan incandescent light 
fibres are made of parchmentized cotton thread, which is afterward 
carbonized. 

Partial Earth. A fault in a conductor caused by imperfect con- 
nection with the earth, where insulation from the earth is desired. 

Passive State. A state of a substance in virtue of which it is 
unattacked by a solvent which ordinarily would dissolve or attack 
it. Iron in strong nitric acid is unattacked or assumes the passive 
state. This particular case is supposed to be due to a coating of 
magnetic oxide, so that there would be properly speaking no 
question of a passive state, but only one of superficial protection. 

The existence of a true passive state of any substance is very- 
doubtful. 

P. D. Abbreviation for potential difference or difference of 
potential, or for electro-motive force. 

Peltier Effect. The thermal effect produced by the passage of 
a current through the junction of two unlike conductors. Such 



STANDARD ELECTRICAL DICTIONARY. 405 

junction is generally the seat of thermo-electric effects, and a current 
is generally produced by heating such a junction. If an independ- 
ent current is passed in the same direction as that of the thermo- 
electric current, it cools the junction, and warms it if passed in the 
other direction. In general terms, referring to thermo-electric 
couples, if passed through them it tends to cool the hot and heat 
the cool junction. The phenomenon does not occur in zinc-cop- 
per junctions. 

Peltier's Cross. A bar of bismuth and a bar of antimony 
soldered centre to centre at right angles, being notched or halved 
there to receive or to set into each other. It is used to demon- 
strate the Peltier effect, q. v. To one pair of ends are connected 
the terminals of a batter}- circuit ; to the other pair are connected 
the terminals of a galvanometer. 

The galvanometer by its deflections in one and then in the other 
direction indicates that the junction is heated when the current 
passes from antimony to bismuth and vice versa. It thus illus- 
trates the heating and cooling of a thermo-electric junction by a 
current of electricity. The current from the battery by the Peltier 
effect either heats or cools the junction, as the case may be. This 
heating or cooling them produces a thermo-electric current in the 
galvanometer circuit. The battery has no direct influence on the 
galvanometer. 

Pendant Cord. A double conductor or pair of conductors, 
insulated from each other and covered with a worsted, silk, or 
cotton covering and used to suspend incandescent lamps and at the 
same time to conduct the current to them. It is also used for 
other similar service, such as acting as conductors for small motors. 
Often each conductor is composed of a number of thin wires laid 
together. This gives flexibility to the cord. 

Synonym— Flexible Cord. 

Pendulum, Electric, (a) A pendulum operated by the inter- 
mittent action of an electro-magnet, whose circuit is opened and 
closed by the pendulum itself. A point at the lower end of the 
pendulum swinging through a globule of mercury may close and 
open the circuit. Various other methods of accomplishing the • 
same end are employed. 

(6) A pith ball suspended by a thread from an insulating 
stand. It is used to show the attraction exercised by a piece of 
sealing wax or other substance excited by rubbing. 

Pen, Electric. A stylus for producing a series of perforations 
in paper, so that the paper may act as a stencil for the reproduc- 
tion of a great number of copies of the original matter. Various 
kinds of electric pens have been invented. One kind, invented by 



406 



STANDARD ELECTRICAL DICTIONARY. 



Edison, consists of a handle carrying an electric motor actuating a 
needle, which is driven in and out of the other end of the handle 
with high rapidity. It is used by being held vertically on the paper 
with the needle end downward, and is moved so as to describe 
perforated letters or designs. The paper is then used as a stencil 
with an ink roller to reproduce the writing or design ad libitum. 




Fig. 256. Electric Pen. 

A simpler kind dispenses with the motor and depends on the per- 
forations produced by the electric spark. As shown in the cut the 
stylus is one terminal of an induction coil circuit. The support 
on which the paper rests is the other terminal and must be a con- 
ductor. In use the induction coil is started, and the stylus is moved 
over the paper ; a series of sparks pass through the paper from 
stylus to the supporting tablet, perforating the paper and produc- 
ing a stencil to be used for reproduction. 

Pentane Standard, Harcourt's. A standard of illuminating 
power ; in it the combustible substance is a gas made by mixing 
one cubic foot of air with three cubic inches of liquid pentane, 
measured at 6o° F. or, if measured as gases, 20 volumes of air to 7 
of pentane. It is burned at the rate of 0.5 cubic foot per hour from 
a cylindrical tube one inch in diameter, closed at the top by a disc 
0.5 inch thick with a hole 0.25 inch in diameter, through which 
the gas issues. It gives a flame 2^ inches high. 

The pentane used is the distillate of petroleum which boils at 
50 C. (122 F.) ; it has a specific gravity at 15 ° C. (6o° F.) of from 
0.628 to 0.631. It is almost pure pentane (C 5 H 12 ). 



STANDARD ELECTRICAL DICTIONARY. 



407 



As long as the rate of consumption is between 0.48 and 0.52 
cubic foot per hour the flame gives practically the same light. 

Perforator. An apparatus used in automatic high speed teleg- 
raphy for perforating strips of paper. These are then used by 
drawing between a roller and contact spring for making and break- 
ing the telegraphic circuit for the production of a record, such as 
the Morse record, at the distant receiving station. 

The perforated strip has different classes of holes punched in 
it to represent dots or dashes. It is fed by machinery very 
rapidly, so that the message is transmitted with the highest speed. 
Several operators may simultaneously prepare the paper strips, and 
thus in conjunction with its rapid feeding in the transmitter, far 
surpass the time of ordinary direct transmission. 





Fig - - 2 57- Perforator for Wheatstone's Automatic Telegraph. 

Perforators may be entirely mechanical but are sometimes 
pneumatic, compressed air being used to operate them. The holes 
they make are on different levels of the paper strip, as shown in 
the cut. 

Period. The time required for the completion of one complete 



408 



STANDARD ELECTRICAL DICTIONARY. 



element of periodic motion. This may be a complete alternation 
(See Alternation, Complete) of an alternating current, or of an 
oscillatory discharge. 

Periodicity. The rate of succession of alternations or of other 
fixed phases ; the rate of recurrence of phenomena. 

Permanency. In electric current conductors the property of 
possessing conductivity unaffected by lapse of time. Generally the 
permanency of conductors is very high. In some cases a slow 
annealing takes place which causes a gradual change with the lapse 
of time. Annealed German silver wire has been found to increase 
in conductivity at about T fo of i per cent, in a year. (Matthiessen.) 
Wire, whether annealed or not, is left in a strained condition after 
the drawing operations, and such a change is consonant with this 
fact. The figure only applies to the samples tested by Mathiessen. 

Permanent State. In a telegraph line or other current con- 
ductor, the condition when a uniform current strength obtains 
over the whole line. When a current is started it advances through 
the line with a sort of wave front gradually increasing in strength. 
At the further end some time may elapse before it attains its full 
intensity. When its does the permanent state prevails. Until 
then the variable state, q. v., exists in the line. 

Permeameter. An apparatus for determining the permeability 
of samples of iron. It consists of a large slotted block of iron. A 
coil is placed within the slot. A hole is 
drilled through one end, and a rod of 
the iron to be tested is passed through 
this hole and through the coil to the 
bottom of the slot. The lower end of 
the rod must be accurately faced off. 
The current is turned on, upon which 
the rod adheres to the bottom of the 
slot. The force required to detach it 
is determined with a spring balance. 
^ B 'lhon k ^ e P ermea tion through its face is pro- 
portional to the square of the force re- 
quired. 

Permeance. The multiplying or the 
conducting power for magnetic lines of 
force possessed by a given mass of 
material. It varies with the shape and 
size of the substance as well as with 
the inducing force. It is distinguished 
from permeability, as the latter is a 
specific quality proper to the material, and expressed as such ; the 



j. -—Spring balance 




Permeameter. 



STANDARD ELECTRICAL DICTIONARY. 409 

permeance is the permeability as affected by size and shape of the 
object as well as by its material. 

Pfluger's Law. A law of electro-therapeutics. It states that 
stimulation of a nerve is only produced by successive appearance 
of the kathelectro tonic state, and disappearance of the anelectro- 
tonic state. 

Phantom Wires. The extra transmission circuits obtained in 
multiplex telegraph systems. A single line arranged for four separ- 
ate simultaneous transmissions by quadruplex apparatus is said to 
establish three phantom wires. 

Phase. In wave motion, oscillating motion, simple harmonic 
motion, or similar periodic phenomena, the interval of time passed 
from the time the moving particle moved through the middle point 
of its course to the instant when the phase is to be stated. 

Pherope. An apparatus for the electric transmission of pictures. 
(See Telephote.) 

Philosopher's Egg. An ellipsoidal vessel mounted with its 
long axis vertical and with two vertical electrodes, the upper one 
sliding, and arranged to be attached to an air pump. A discharge 
through it when the air is exhausted takes the general shape of 
an egg. 

Phonautograph. An apparatus for registering the vibrations of 
a stylus, which is mounted on a diaphragm and is acted on by 
sound waves. 

It is virtually a resonating chamber, over one of whose ends a 
parchment diaphragm is stretched. To the centre of the parchment 
a needle or stylus is attached. A cylinder covered with soot is 
rotated in contact with the point of the stylus. As the chamber 
is spoken into the diaphragm and stylus vibrate and the vibra- 
tions are marked on the cylinder. It is of some electric interest in 
connection with telephony. 

Phone. Colloquial abbreviation for telephone. 

Phonic Wheel. A form of small motor of very simple con- 
struction. It consists of a toothed wheel of soft iron. A bar 
electro-magnet is fixed with one pole facingthe teeth of the wheel. 
By a tuning fork make and break a succession of impulses of rapid 
frequency and short duration are sent through the magnet. The 
teeth act as armatures and are successively attracted by the magnet. 
The regulated speed is one tooth for each impulse, but it may rotate 
at one-half the speed, giving two teeth for each impulse, or at cer- 
tain other sub-multiples of its regular speed. It is the invention of 
Paul Lecour. 



410 STANDARD ELECTRICAL DICTIONARY. 

Phonograph. An apparatus fcr reproducing articulate speech. 
It is not electric, except as it may be driven by electricity. 

It consists of a cylinder of wax-like material which is rotated and 
moved slowly, longitudinally, screw fashion, at an even speed. A 
glass diaphragm carrying a needle point is supported with the 
point barely touching the wax. If the diaphragm is agitated, as 
by being spoken against, the needle is driven back and forwards 
cutting a broken line or groove following the direction of the 
thread of a screw in the wax, the depth of which line or groove 
continually varies. 

This imprints the message. If the needle is set back and the . 
cylinder is rotated so as to carry the needle point over the line 
thus impressed, the varying depth throws the needle and diaphragm 
into motion and the sound is reproduced. 

The cylinder is rotated often by an electric motor, with a cen- 
trifugal governor. 

Phonozenograph. An apparatus for indicating the direction of 
the point where a sound is produced. It operates by a microphone 
and telephone in conjunction with a Wheatstone bridge to determine 
the locality. 

Phosphorescence. The emission of light rays by a substance not 
heated, but whose luminosity is due to the persistence of luminous 
vibration after light has fallen upon it. 

A phosphorescent body, after exposure to light, is luminous 
itself. Phosphorescence maybe induced by rubbing or friction, by 
heat, by molecular bombardment, as in Crookes' tubes, and by static 
discharge of electricity, as well as by simple exposure to light. 

Another form of phosphoresence may be due to slow chemical 
combustion. This is the cause of the luminosity of phosphorous. 

Phosphorous, Electrical Reduction of. Phosphorous is reduced 
from bone phosphate by the heat of the electric arc. The phos- 
phate mixed with charcoal is exposed to the heat of the voltaic arc, 
and reduction of the phosphorous with its volatilization at once 
ensues. The phosphorous as it volatilizes is condensed and 
collected. 

Photo=eIectricity . The development of electrical properties by 
exposure to light. Crystals of fluor spar are electrified not only 
by heat (see Pyro-electricity) but also by exposure to sunlight or 
to the light of the voltaic arc. 

Photo = electric Microscope. A projection, solar or magic 
lantern microscope worked by the electric light. 

Photo=electro=motive Force. Electro-motive force produced 
in a substance by the action of light. 



STANDARD ELECTRICAL DICTIONARY. 411 

Photometer. An apparatus for measuring the intensity of light 
emitted by a given lamp or other source of illuminating power. 
They may be classified into several types. 

Calorimetric or Heat Photometers act by measuring relatively 
the heat produced by the ether waves (so-called radiant heat) 
emitted by the source. The accuracy of the instrument is increased 
by passing the rays through an alum solution. A thermopile, or 
an air thermometer, may be used to receive the rays. 

Chemical Photometers. In these the light falls upon sensitized 
photographic paper. The depth of coloration is used as the index 
of illuminating power. 

Direct Visual Photometers. These include Rumford's Shadow 
Photometer, Bunsen's Bar Photometer , and Wheatstone's Bead 
Photometer, in which the light is estimated by direct visual com- 
parison of its effects. 

Optical Photometers. These include Polarization Photometers, 
in which the light is polarized ; Dispersion Photometers, in which 
a diverging lens is placed in the path of the rays of light so as to 
reduce the illuminating power in more rapid ratio than that of the 
square of the distance. 

Selenium Photometers , in which the variations in resistance of 
selenium as light of varying intensity falls upon it is used as the 
indicator of the intensity of the light. 

Jet Photometers, for gas only, in which the height of a flame 
under given conditions, or the conditions requisite to maintain a 
flame of given height, is used to indicate the illuminating power. 

The subject of photometers has acquired more importance than 
ever in view of the extensive introduction of the electric light. 
(See Candle, Standard — Carcel — Violas Standard — and Photom- 
eters of various kinds.) 

Photometer, Actinic. A photometer whose registrations are 
produced by the action of the light being tested upon sensitized 
paper or plates, such as used in photography. Some efforts at self- 
registering photometers have been based on actinic registration of 
the height of a flame of the gas to be tested. 

Photometer, Bar. A photometer in which the two lights to be 
compared are fixed at or opposite to the ends of a bar or scale of 
known length, generally 60 or 100 inches. The bar is divided by 
the rule of the inverse square of the distances, so that if a screen is 
placed on any part of the bar where it receives an equal amount of 
light from both sources, the figure on the bar will indicate the rela- 
tive illuminating power of the larger lamp or light in terms of the 
smaller. The divisions of the bar are laid out on the principle that 
the illuminating power of the two sources of light will vary inversely 
with the square of their distance from the screen. 



412 STANDARD ELECTRICAL DICTIONARY. 

The screen used is sometimes the Bunsen disc. This is a disc 
of paper with a spot of paraffine wax in the centre melted thoroughly 
into the paper or with a ring of paraffine wax surrounding the 
untouched centre. When this disc is equally illuminated on both 
sides the spot is nearly invisible. Inequality of illumination 
brings it out more visibly. Sometimes a Iyeeson disc is used. This 
consists of three pieces of paper, two thin ones between which a 
thicker piece, out of which a star is cut, is laid. When equally illu- 
minated on both sides the star appears equally bright on both sides. 

The bar photometer is the stardard form. A candle or pair of can- 
dles may be burned at one end and' an incandescent lamp at the 
other, or a gas flame may first be rated by candles and used as a 
standard. 

Synonyms — Bunsen 's Photometer — Translucent Disc Photometer. 



Fig. 259. Bar Photometer. 

Photometer, Calorimetric. A photometer in which the radiant 
energy, so called radiant heat, is used as the measurer of the light. 

In one type a differential air thermometer is used, one of whose 
bulbs is blackened. On exposing this bulb to a source of light it 
will become heated, and if lights of the same character are used 
the heating will be in proportion to their illuminating power quite 
closely. The heating is shown by the movements of the index. 
By careful calibration the instrument may be made quite reliable. 

Photometer, Dispersion. A photometer in which the rays from 
one of the lights under comparison are made more divergent by a 
concave lens. In this way a strong light, such as an arc lamp can be 
photometered more readily than where only the natural divergence 
of the beam exists. The law of the variation of the intensity of 
light with the square of the distance is abrogated for a law of more 
rapid variation by the use of a concave lens. 

The diagram, Fig. 260, illustrates the principle. E represents a 
powerful light, an arc light, to be tested. Its distance from the 
screen is e. Its light goes through the concave lens L and is dis- 
persed as shown over an area A 1 , instead of the much smaller area 
A, which the same rays would otherwise cover. Calling / the dis- 
tance of the lens from the screen,/ its focus, and c the distance of 
the standard candle from the screen when the shadows are of equal 
intensity, we have the proportion. 



STANDARD ELECTRICAL DICTIONARY. 



4i3 



Illuminating power of lamps : ditto of standard candle : : / (e- 
l) -fef : (c/r 




Fig. 260. Diagram of Principle of the Dispersion Photometer. 

The cut, Fig. 261, gives a perspective view of Ayrton's Dis- 
persion Photometer. Cis the standard candle, L the concave lens, 




Fig. 261. Ayrton's Dispersion Photometer. 

R the rod for producing the two shadows on the screen 5. The 
mirror M is fixed at an angle of 45 ° with the stem on which it 
rotates. The light of the arc lamp is received by the mirror and is 
reflected through the lens. The candle holder slides along a grad- 
uated bar G, and at D is an index plate to show the angle at which 
the spindle carrying the mirror is set. 



4i4 



STANDARD ELECTRICAL DICTIONARY. 



Dr. J. Hopkinsonin his dispersion photometer uses a double con- 
vex lens. This gives a focal image of the arc-lamp between the 
lens and screen, whence the rays diverge very rapidly, thus giving 
the desired dispersion effect. 

It is principally for arc lamps that dispersion photometers are 
used. 



Photometer, Shadow 




which the relative 



Fig. 262. Rumford's Shadow Photometer. 

intensity of the two lights is estimated by the intensity or strength 
of shadows of the same object which they respectively cast. 




Fig. 263. 
A rod is supported in a vertical position. 



Rumford's Shadow Photometer Arranged for Testing 
Incandescent Lamps. 

Back of it is a screen 



STANDARD ELECTRICAL DICTIONARY. 415 

of white paper. The two lights to be compared are arranged in 
front of the rod and at a little distance from each other. They 
are shifted about until the two shadows appear of equal darkness. 
The relative intensity of the lights varies inversely with the square 
of their distances from the shadows cast, respectively by them on 
the screen. 

The cut, Fig. 262, shows the simplest type of the shadow photo- 
meter. In the cut, Fig. 263, a shadow photometer for testing 
incandescent lamps is shown. In it E is the lamp under trial sup- 
ported by a clamp H. A is an ampere meter in circuit with the 
lamp, and Fis a voltmeter. A candle C can be moved along a 
graduated scale G G. R is the vertical rod, and S is the screen on 
which the shadows fall. 

Photophore. An instrument for medical examination of the 
cavities of the body. It includes an incandescent lamp mounted 
in a tube with a concave mirror and convex lens. 

Photo = voltaic Effect. The change in resistance of some sub- 
stances effected by light. Selenium, of all substances, is most 
susceptible to this effect. (See Selenium.) 

Piano, Electric. A piano whose manual or key -board operates 
to close electric circuits, whereby electro-magnets are caused to 
operate to drive the hammers against the strings. 

Pickle. An acid solution for cleaning metal surfaces before 
electro-plating, galvanizing or other deposition of metal upon 
them. 

Picture, Electric. A picture produced by passing a strong dis- 
charge through a piece of gold leaf clamped or firmly pressed upon 
a sheet of paper: The gold leaf is cut out of the desired shape, or 
else a stencil of paper overlays it. The discharge dissipates the 
gold, and produces a purple colored reproduction of the design 
upon the paper. The design is due to the deposition of an exceed- 
ingly thin film of metallic gold. 

Synonym — Electric Portrait. 

Pile. A galvanic or voltaic battery. It is sometimes restricted 
to a number of voltaic couples connected. It should be only 
applied to batteries with superimposed plates and no containing 
vessel such as the Dry Pile, q. v., or Volta's Pile, q. v. 

Pilot Transformer. In alternating current distribution a 
small transformer placed at any part of the system and connected 
to a voltmeter in the central station, to indicate the potential 
difference of the leads. 

Pilot Wires. Wires brought from distant parts of electric light 
or power mains, and leading to voltmeters at the central station, so 



416 STANDARD ELECTRICAL, DICTIONARY. 

that the potential of distant parts of the system can be watched. 
The wires can be very small, as they have but little current to 
transmit. 

Pistol, Electric. An experimental apparatus for exhibiting the 
power of electric incandescence or of the electric spark. A tube 
is mounted with a handle like a pistol. A plug is provided to 
screw in and out of its side. The plug carries two wires connected 
on its inner side by a fine platinum wire, or else disconnected but 







Fig". 264. Electric Pistol. 

with their ends brought near together to act as terminals for the 
production of a spark. To use it the tube is filled with a mixture 
of air and gas, the latter either hydrogen, hydro-carbon or other 
combustible gas. The tube when full is corked. The wire is 
heated to incandescence by a current, or a spark is passed from a 
Leyden jar or other source of electrostatic excitation. The mix- 
ture, if properly proportioned, explodes and expels the cork vio- 
lently. 

Pith. A light and soft cellular tissue forming the central core of 
exogenous trees and plants. In the older parts of the tree the woody 
tissue often encroaches in and partly obliterates it. 

For electrical pith-balls, the pith of the elder, of corn, or, best 
of all, of sun-flower stems is used. 

Pith=balls. Ball made of pith. They are used in the construc- 
tion of electroscopes and for other experiments in static electricity. 

They are cut out with a sharp knife and their shape may be 
improved by gentle rolling in the hand or between the fingers. 

Pivot Suspension. Suspension poising or supporting of an 
object on a sharp pivot. This is used for the needle in the ordinary 
compass. A cavity or inverted cup, which may be made of agate, 
is attached to the middle of the needle which has a hole for its 



STANDARD ELECTRICAL DICTIONARY. 417 

reception. The centre of gravity of the needle comes below the 
bottom of the cup. 

Pivot suspension is not perfect, as it has considerable friction. 
There is no restitution force, as with torsion filaments. 

Plant. The apparatus for commercial manufacturing or technical 
works. An electric lighting plant includes the boilers, engines 
and dynamos for producing the current, and the electric mains and 
subsidiary apparatus. 

Plant Electricity. Electricity manifested by plant life. By 
means of a galvanometer potential differences are found to exist 
in different parts of trees or fruits. The roots and interior portions 
are negative, and the flowers, smaller branches and fruit are 
positive. 

In some cases a contraction of the tissue of plants can be pro- 
duced by an electric current. The sensitive plant and others 
exhibit this phenomenon, exactly analogous to the action of mus- 
cular tissue. 

Plate, Arrester. In a lightning arrester the plate connected to 
the circuit. Sometimes both plates are designated arrester plates. 

Plate Condenser. A static condenser having a flat plate of glass 
for dielectric. (See Epinus* Condenser.) 

Plate Electrical Machine. A frictional electric machine, in 
which a circular plate of glass is excited by friction with the 
cushions. It is the most recent type of frictional machine and has 
superseded the old cylinder machines. In its turn it is superseded 
by influence machines, really plate machines, but not so termed 
in practice. 

Plate, Ground. In a lightning arrester, the plate connected to 
the earth. 

Plate, Negative. In a voltaic battery, either primary or secondary, 
the plate which is unattacked by the oxygen or negative radical or 
element of the fluid. It corresponds to the carbon plate in the 
ordinary voltaic battery, and is the one charged with positive 
electricity. 

Plate, Positive. In a voltaic battery, either primary or secondary, 
the plate which is dissolved or attacked by the oxygen or negative 
radical or element of the fluid. It is the plate corresponding to 
the zinc plate in the ordinary voltaic battery, and is the one 
charged with negative electricity. 

Plating Balance. A balance or scales to which articles in an 
electroplater's bath are suspended. A weight exceeding by a 
known amount that of the article as immersed overbalances the 



418 STANDARD ELECTRICAL DICTIONARY. 

article. When the plating is being deposited as soon as it exceeds 
the excess of weight of the counterpoise the balance tips, the article 
descends a little, the electric circuit is broken and the plating 
ceases. Thus the plating is automatically stopped when a prede- 
termined amount of metal is deposited. 

Plating Bath. A vessel of solution for the deposition of metal 
by electrolysis as used in electro-plating. 

Plating, Electro=. The deposition of metal by electrolysis so 
as to coat the conducting surface of objects therewith. The full 
details of the many processes are very lengthy and cannot be given 
here. 

The general principle includes a battery or source of electric 
current. The object to be plated is connected to the negative ter- 
minal and is immersed in the solution. Thus with a battery the 
object is in electrical connection with the zinc plate. To the other 
terminal a metallic plate is connected. The object and the plate 
termed the anode being introduced into a suitable bath, the metal 
whose solution is in the bath is deposited upon the surface of the 
object. 

The bath is a solution of the metal in some form that will lend 
itself to the electrolytic action. The anode is often a plate of the 
metal of the bath, so that it dissolves as fast as metal is deposited on 
the object, thus keeping up the strength of the solution. 

The objects to be plated must be scrupulously clean, and great 
care must be taken to keep the bath uncontaminated. 

When the object has a non-conducting surface, it is made con- 
ducting by being brushed over with plumbago. In addition iron 
dust is sometimes dusted over it. This acts by precipitating the 
metal of the bath directly and thus giving a conducting basis for 
the metal to deposit on. To avoid getting iron in a bath the object 
may be dipped in copper sulphate solution. This precipitates cop- 
per in place of the iron and leaves the article in good shape for 
silver or other plating. 

Electro-plating, if made thick enough, gives a reverse of the 
article when separated therefrom. A direct copy can be got by a 
second plating, on the first plating after separation, or a wax im- 
pression can be employed. 

Under the different metals, formulae for the baths will be found. 
(See also Quicking — Steeling — Plating Balance,) 

Platinoid. An alloy of copper, nickel, zinc in the proportions 
of German silver with i or 2 per cent of tungsten. It is used 
for resistances. It has a specific resistance (or resistance per 
centimeter cube) of about 34 microhms. Its percentage variation 
in resistance per degree C. (i.8° F.) is only about .021 per cent., 



STANDARD ELECTRICAL DICTIONARY. 



419 



or less than half that of German silver. This is its most valuable 
feature. 

Platinum. A metal ; one of the elements ; symbol, Pt ; atomic 
weight, 197.4 ; equivalent, 49.35 ; valency, 4 ; specific gravity, 21.5. 
It is a conductor of electricity. The following data refer to the 
annealed metal at o° C. (32 F.) 

Relative Resistance (Silver annealed = 1), 6.022 

Specific Resistance, 9«057 microhms. 

Resistance of a wire, 

(a) 1 foot long, weighing 1 grain, 2.779 ohms. 

(b) 1 foot long, 1-1000 inch thick, 54-49 " 

(c) 1 meter long, weighing 1 gram, 1-938 " 

(d) 1 meter long, 1 millimeter thick, -H53 " 
Resistance of a 1 inch cube, 3-565 mich, 
Electro-chemical equivalent (Hydrogen = .0105), .5181. 

The coefficient of expansion by heat is almost the same as that 
of glass. It can be passed through holes in glass and the latter 
can be melted about it so as to hermetically seal its place of passage 
through the glass. It is used in incandescent lamps for leading-in 
wires and other similar uses. 

Platinum Black. Finely divided platinum. It is made by boil- 
ing a solution of platinic chloride with excess of sodium carbonate 
and a quantity of sugar, until the precipitate is perfectly black and 
the supernatant liquid is colorless. It seems to possess a great 
power of occluding oxygen gas. When heated to redness it becomes 
spongy platinum. The negative plates of a Smee battery are coated 
with platinum black. 

Platinum =silver Alloy. An alloy of 1 part platinum and 2 
parts silver, used for resistance coils. 

Relative Resistance (silver annealed = 1), 16.21 

Specific Resistance at o°C. (32 F.), 24.39 mich. 

Resistance of a wire, 

(a) 1 foot long, weighing 1 grain, 4-197 ohms. 

(b) 1 foot long, 1- 1000 inch diameter, 146.70 " 

(c) 1 meter long weighing 1 gram, 2.924 " 

(d) 1 meter long, 1 millimeter diameter, 0.3106 " 
Resistance of a 1 inch cube, 9-603 microhms. 
Percentage Variation per degree C. (i.8° F.) at about 20 C. 

(68° F.), 0.031 per cent. 
Synonym — Platinum Alloy. 

Platinum Sponge. Finely divided platinum obtained by ignit- 
ing platinum black, q. v., and also by igniting salts of platinum. 
It has considerable power of condensing or occluding oxygen. It 



420 



STANDARD ELECTRICAL DICTIONARY. 



will, if in good condition, set fire to a jet of hydrogen impinging 
npon it. 

Plow. Contact arms projecting downwards from the motors, 
trucks, or bodies of electric street cars, which enter the under- 
ground conduit through the slot and carry contact pieces or 
brushes, to take the current for driving the motors from the leads 
within the conduit. 

Plucker Tubes. A special form of Geissler tube designed for 
the production of stratification and for observing the effects pro- 
duced in the space surrounding the negative electrode. 

Plug, (a) A piece of metal with a handle and a somewhat tapered 

end, used to make connections by 
insertions between two plates or 
blocks of metal slightly separated 
and with grooves to receive it. 

(b) A plug or wedge with two 
metallic faces, insulated from each 
other with a separate wire con- 
nected to each one. It is used in 
spring-jacks q. v., to introduce a 
loop in a circuit. 
Synonym — Wedge. 

Plug. v. To connect by inserting 
a plug, as in a resistance box. 

Plug, Double. A spring- jack 
plug or wedge with two pairs of in- 
sulated faces, one behind the other, 
so as to simultaneously introduce two loops into a circuit. 

Plug, Grid. A piece or mass of lead oxide, inserted into the 
holes in the lead plates of storage batteries. The holes are often 
dovetailed or of uneven section to better retain the plugs. 

Plug Infinity. In a box-bridge or resistance box, a plug 
whose removal from between two disconnected 
discs opens the circuit. All the other discs are 
connected by resistance coils of various resist- 
ance. 




Plugs for Resistance 
Coil Box. 




Plug Switch. A switch composed of two 
contact blocks, not touching each other and 
brought into electrical connection by the inser- 
tion of a metallic plug. The latter is usually 
provided with an insulating handle, and a seat 
is reamed out for it in the two faces of the contact blocks. 



Fig. 266. Plug 
Switch. 



STANDARD ELECTRICAL DICTIONARY. 



421 



Plumbago. Soft lustrous graphite, a native form of carbon ; 
sometimes chemically purified. It is used in electro-plating to 
give a conducting surface to non-conducting objects, such as wax 
moulds. The surface, after coating with plumbago, is sometimes 
dusted over with iron dust, which pre- 
cipitates the metal of the bath and 
starts the plating. It is sometimes 
plated with copper, silver or gold, and 
is then termed coppered, silvered, or 
gilt plumbago. It is gilded by moisten- 
ing with etherial solution of gold 
chloride and exposing to the air, and 
drying and igniting. 

Plunger. A movable core which is 
used in connection with a so-called 
solenoid coil, to be drawn in when the 
coil is excited. (See Coil and Plunger.) 

P. 0. Abbreviation for Post Office, 
q. v. 

Poggendorfs Solution. An acid 

depolarizing and exciting fluid for zinc- 
carbon batteries. The following is its 
formula : Water, 100 parts ; potassium 
bichromate, 12 parts ; concentrated 
sulphuric acid, 25 parts. All parts by 
weight. Use cold. 

Point, Neutral, (a) On a commu- 
tator of a dynamo the points at the 
ends of the diameter of commutation, 
or where the brushes rest upon the 
surface of the commutator, are termed 
neutral points. At these points there 
is no generation of potential, they 
marking the union of currents of op- 
posite direction flowing from the two 
sides of the armature into the brushes. 

(b) In electro-therapeutics, a place 
in the intra-polar region of a nerve so 
situated with reference to the kathode 
and electrode as applied in treatment, 
that its condition is unaffected. 

Synonym — Indifferent Point. 




Fig. 267. Coil and Plunger 

with Scales to Show 

Attraction. 



(c) In a magnet the point ol no attraction, situated between 



422 STANDARD ELECTRICAL DICTIONARY. 

the two poles, at about an equal distance from each, so as to mark 
the centre of a magnet of even distribution of polarity. 

(d) In thermo-electricity the point of temperature where the 
thermo-electric powers of two metals are zero ; in a diagram the 
point where the lines representing their thermo-electric relations 
cross each other ; if the metals are arranged in a thermo-electric 
couple, one end at a temperature a given amount above, the 
other at a temperature the same amount below the neutral point, 
no current or potential difference will be produced. 

Point, Null. A nodal point in electrical resonators ; a point 
where in a system of waves or oscillations, there is rest, the zero of 
motion being the resultant of oppositely directed and equal 
forces. In electrical resonators it is to be sought for in a point 
symmetrically situated, with reference to the spark gap, or in a 
pair of points, which pair is symmetrically placed. 

The null point in resonators is found by connecting a lead from 
one of the secondary terminals of an induction coil to different 
parts of the resonator. The null point is one where the connection 
does not give rise to any sparks between the micrometer knobs or 
spark gap, or where the sparks are of diminished size. 

The whole is exactly comparable to loops and nodes in a vibrating 
string or in a Chladni plate as described in treatises on sound and 
acoustics. (See Resonance, Electrical — Resonator, Electrical.) 

Synonym — Nodal Point. 

Point Poles. Magnet poles that are virtually points, or of no 
magnitude. A long thin magnet with little leakage except close 
to the ends may be supposed to have point poles within itself a 
short distance back from the ends. 

Points, Consequent. In a magnet with consequent poles, the 
points where such poles are situated. 

Points, Corresponding. In bound electrostatic charges the 
points of equal charges of opposite potentials ; the points at oppo- 
site extremities of electrostatic lines of force. This definition 
implies that the bound charges shall be on equal facing areas of 
conductors, as otherwise the spread or concentration of the lines of 
force would necessitate the use of areas of size proportionate to the 
spreading or concentrating of the lines of force. At the same time 
it may figuratively be applied to these cases, the penetration of the 
surface by a single line of force including the area fixed by its 
relation to the surrounding lines. 

Points, Isoelectric. In electro-therapeutics, points of equal 
potential in a circuit. 



STANDARD ELECTRICAL DICTIONARY. 423 

Points of Derivation. The point where a single conductor 
branches into two or more conductors, operating or acting in 
parallel with each other. 

Polar Angle. The angle subtended by one of the faces of the 
pole pieces of the field-magnet of a dynamo or motor. The centre 
of the circle of the angle lies in the axis of the armature. 

Synonym — Angle of Polar Span. 

Polar Extension. An addition made of iron to the poles of 
magnets. Various forms have been experimented with. The pole 
pieces of dynamo field magnets are polar extensions. 

Synonyms — Pole Piece — Polar Tips. 

Polarity, Diamagnetic. The induced polarity of diamagnetic 
substances ; it is the reverse of paramagnetic polarity, or of the 
polarity of iron. A bar of diamagnetic material held parallel with 
the lines of force in a magnetic field has a like pole induced in the 
end nearest a given pole of the field magnet, and vice versa. This 
theory accounts for the repulsion by a magnet of a diamagnetic 
substance. The existence of this polarity is rather an assumption. 
It originated with Faraday. 

Polarity, Paramagnetic. The induced polarity of paramag- 
netic substances, such as iron, nickel, or cobalt. 

When such a substance is brought into a magnetic field the part 
nearest a specific pole of a magnet acquires polarity opposite to 
that of such pole and is thereby attracted. 

Another way of expressing it, in which the existence of a pole 
in or near to the field is not implied, is founded on the conventional 
direction of lines of force. Where these enter the substance a 
south pole is formed and where they emerge a north pole is formed. 

Such polarity tends always to be established in the direction of 
greatest length, if the body is free to rotate. 

Polarization, (a) The depriving of a voltaic cell of its proper 
electro-motive force. Polarization may be due to various causes. 
The solution may become exhausted, as in aSmee battery, when 
the acid is saturated with zinc and thus a species of polarization 
follows. But the best definition of polarization restricts it to the 
development of counter-electro-motive force in the battery by the 
accumulation of hydrogen on the negative (carbon or copper) plate. 
To overcome this difficulty many methods are employed. Oxidiz- 
ing solutions or solids are used, such as solution of chromic acid 
or powdered manganese dioxide, as in the Bunsen and Leclanche 
batteries respectively ; a roughened surface of platinum black is 
used, as in the Smee battery ; air is blown through the solution to 
carry off the hydrogen, or the plates themselves are moved about 
in the solution. 



424 STANDARD ELECTRICAL DICTIONARY. 

(b) Imparting magnetization to a bar of iron or steel, thus mak- 
ing a permanent magnet, is the polarization of the steel of which 
it is made. Polarization may be permanent, as in steel, or only 
temporary, as in soft iron. 

(c) The strain upon a dielectric when it separates two oppositely 
charged surfaces. . The secondary discharge of a Ley den jar, and 
its alteration in volume testify to the strain put upon it by charging. 

(d) The alteration of arrangement of the molecules of an elec- 
trolyte by a decomposing current. All the molecules are supposed 
to be arranged with like ends pointing in the same direction, posi- 
tive ends facing the positively-charged plate and negative ends 
the negatively ^charged one. 

(e) The production of counter-electro-motive force in a secondary 
battery, or in any combination capable of acting as the seat of 
such counter-electro-motive force. (See Battery, Secondary — Bat- 
tery > Gas.) The same can be found often in organized cellular tissue 
such as that of muscles, nerves, or of plants. If a current is passed 
through this in one direction, it often establishes a polarization or 
potential difference that is susceptible of giving a return current 
in the opposite direction when the charging battery is replaced by 
a conductor. 

Polarization Capacity. A voltaic cell in use becomes polarized 
by its negative plate accumulating hydrogen, or other cause. This 
gradually gives the plate a positive value, or goes to set up a counter- 
electro-motive force. The quantity of electricity required to produce 
the polarization of a battery is termed its Polarization Capacity 
or Capacity of Polarization. 

Polarization of the Medium. The dielectric polarization, q. v., 
of a dielectric, implying the arrangement of its molecules in chains 
or filaments ; a term due to Faraday. He illustrated it by placing 
filaments of silk in spirits of turpentine, and introduced into the . 
liquid two conductors. On electrifying one and grounding (or 
connecting to earth) the other one, the silk filaments arranged 
themselves in a chain or string connecting the points of the con- 
ductors. 

Polar Region. That part of the surface of a magnet whence the 
internal magnetic lines emerge into the air. (S. P. Thompson.) As 
such lines may emerge from virtually all parts of its surface, the 
polar regions are indefinite areas, and are properly restricted to the 
parts whence the lines emerge in greatest quantity. 

Polar Span. A proportion of the circle which represents the 
transverse section of the armature space between the pole pieces of 
the field magnet in a dynamo or motor ; it is the proportion 
which is filled by the faces of the pole pieces. 



STANDARD ELECTRICAL DICTIONARY. 425 

Pole, Analogous. The end of a crystal of a pyroelectric sub- 
stance, such as tourmaline, which end when heated become posi- 
tively electrified. On reduction of temperature the reverse effect 
obtains. 

Pole, Antilogous. The end of a crystal of a pyroelectric sub- 
stance, such as tourmaline, which end, while increasing in temper- 
ature, becomes negatively electrified. During reduction of its 
temperature the reverse effect obtains. 

Pole Changer, (a) An automatic oscillating or vibrating switch 
or contact-breaker which in each movement reverses the direction 
of a current from a battery or other source of current of fixed 
direction, as such current goes through a conductor. 

(b) A switch moved by hand which for each movement effects 
the above result. 

Pole, Negative, (a) In a magnet the south pole ; the pole into 
which the lines of force are assumed to enter from the air or outer 
circuit. 

(b) In a current generator the pole or terminal into which the 
current is assumed to flow from the external circuit. It is the 
negatively charged terminal and in the ordinary voltaic battery is 
the terminal connected to the zinc or positive plate. 

Pole Pieces. The terminations of the cores of field or other 
electro-magnets, or of permanent magnets. These terminations 
are variously shaped, sometimes being quite large compared to 
the core proper of the magnet. 

They are calculated so as to produce a proper distribution of and 
direction of the lines of force from pole to pole. As a general rule 
the active field should be of uniform strength and the pole pieces 
may be of contour calculated to attain this end. 

Pole, Positive, (a) In a magnet the north pole ; the pole from 
which lines of force are assumed to emerge into the air. 

(b) In a current generator the pole or terminal whence the cur- 
rent is assumed to issue into the outer circuit. It is the positively 
charged terminal, and in the ordinary voltaic battery is the terminal 
connected to the copper or carbon plate, termed the negative plate. 

Poles, (a) The terminals of an open electric circuit, at which 
there necessarily exists a potential difference, produced by the gen- 
erator or source of electro-motive force in the circuit. 

(b) The terminals of an open magnetic circuit ; the ends of a 
magnetized mass of steel, iron or other paramagnetic substance. 

(c) The ends in general of an}^ body or mass which show electric 
or magnetic properties more developed than those of the central 
sections of the body. 



426 



STANDARD ELECTRICAL DICTIONARY. 



Pole, Salient. In dynamo and motor field magnets, salient 
poles are those projecting from the base or main body of the field 




Fig. 268. Salient Poles of Field Magnet. 

magnet, as distinguished from consequent poles formed by coils 
wound on the main body itself. 

Poles, Compensating. A device for avoiding the cross-mag- 
netizing effect on the commutator core due to the lead of the 
brushes. It consists in maintaining a small bar electro-magnet 
perpendicularly between the pole pieces. This compensates the 
cross-magnetizing effect. 

Poles of Intensity. The locus of highest magnetic force on the 
earth's surface. One such pole is in Siberia, another is about lat. 
52 N., long. 92 ° W. 

Poles of Verticity. The magnetic poles of the earth. (See 
Magnetic Poles.) 

Pole Tips. The extreme ends of the expanded poles of a field 
magnet. In some machines some of the pole tips are made of cast 
iron, to alter the distribution of the lines of force and resulting 
magnetic pull upon the armatures. This is done to take off the 
weight of the armature from its bearings. 

Pole, Traveling. A term applied to the poles produced in the 
action of a rotatory field, whose poles constantly rotate around the 
circle of the field. (See Field, Rotatory.) 

Porous Cup. A cup of pipe clay, unglazed earthenware or 



STANDARD ELECTRICAL DICTIONARY. 427 

other equivalent material used in voltaic cells to keep two liquids 
separate and yet to permit electrolysis and electrolytic conduction. 

They are necessarily only an expedient, as their porous nature 
permits considerable diffusion, and were they not porous electro- 
lytic action would be impossible. 

Synonym — Porous Cell. 

Porret's Phenomenon. In electro-physiology, an increase in 
the diameter of a nerve produced by the positive pole of a voltaic 
circuit, when placed in contact with the tissue and near to the 
nerve in question, the other pole being connected to a more or less 
remote part of the body. 

Portelectric Railroad. A railroad worked by solenoidal attrac- 
tion, the car forming the core of the solenoids. It includes a series 
of solenoids or hollow coils of copper wire distributed all along the 
road and inclosing within themselves the track. On this a cylin- 
drical car with pointed ends moves on wheels. Current is supplied 
to the solenoid in advance of the car, and attracts it. As it advances 
it breaks the contacts of the attracting solenoid and turns the cur- 
rent into the one next in advance. This operation is repeated as 
the car advances. 

The solenoids are placed close together, each including in the 
trial track 630 turns of No. 14 copper wire. The car was of wrought 
iron, 12 feet long, 10 inches in diameter and weighing 500 lbs. It 
was proposed to employ the system for transportation of mail 
matter and similar uses. Synonym— Tachyphore. 

Position Finder. An instrument for determining the position 
of objects which are to be fired at from forts. It is designed for 
use from forts situated on the water. 

Fiske's position finder may be thus generally described. On a 
chart the channel is divided into squares, and the position finder 
determines the square in which a vessel lies. For each square the 
direction and elevation of the guns is calculated beforehand. The 
enemy can therefore be continuously located and fired at, although 
from smoke or other cause the object may be quite invisible to the 
gunner. 

It comprises two telescopes situated at distant extremities of as 
long a base line as is obtainable. These telescopes are kept directed 
upon the object by two observers simultaneously. The observers 
are in constant telephonic communication. As each telescope 
moves, it carries a contact over an arc of conducting material. 
Below each telescope is an arm also moving over an arc of con- 
ducting material. These arcs enter into a Wheatstone bridge and 
are so connected that when the arm and the distant telescope are 
at the same angle or parallel a balance is obtained. Thus each 



428 STANDARD ELECTRICAL DICTIONARY. 

observer has the power of establishing a balance. A chart is pro- 
vided for each of them, and over it the arm connected with the 
distant telescope and an arm or indicator attached to the telescope 
at that station move so that as long as both telescopes point at the 
object and each observer maintains the electric balance, the inter- 
section of the arms shows the position on the chart. 

The Position Finder is a simplification and amplification of the 
Range Finder, q. v. In practice the observers may be placed far 
from the forts, and may telephone their observations thereto. It 
has been found accurate within one-third of one per cent. 

Positive Direction. The direction which lines of force are 
assumed to take in the air or outer circuit from a positive to a 
negative region. It applies to electrostatic, to magnetic and to 
electro-magnetic lines of force. 

Positive Electricity. The kind of. electricity with which a 
piece of glass is charged when rubbed with silk ; vitreous electricity. 

In a galvanic cell the surface of the copper or carbon plate is 
charged with positive electricity. (See Electrostatic Series.) 

According to the single fluid theory positive electrification con- 
sists in a surplus of electricity. 

Post Office, adj. Many pieces of electric apparatus of English 
manufacture are thus qualified, indicating that they are of the 
pattern of the apparatus used by the British Post Office in its tele- 
graph department. 

Potential. Potential in general may be, treated as an attribute of 
a point in space, and may express the potential energy which a 
unit mass would have if placed at that point. 

This conception of potential is that of a property attributable to 
a point in space, such that if a unit mass were placed there the 
forces acting upon it would supply the force factor of energy, 
while the body would supply the mass factor. This property is 
expressible in units, which produce, if the supposed mass is a unit 
mass, units of work or energy, but potential itself is neither. 

Thus taking gravitation, a pound mass on the surface of the 
earth (assuming it to be a sphere of 4,000 miles radius) would 
require the expenditure of 21,120,000 foot pounds to remove it to 
an infinite distance against gravity. The potential of a point in 
space upon the surface of the earth is therefore negative and is 
represented by — 21,120,000 X 32.2 foot poundals (32.2 '— accelera- 
tion of gravity). (See Poundal.) In practice and conventionally 
all points on the earth's surface are taken as of zero potential. 

Potential, Absolute. The absolute electrical potential at a 
point possesses a numerical value and measures the tendency 



STANDARD ELECTRICAL DICTIONARY. 429 

which the existing electric forces would have to drive an electrified 
particle away from or prevent its approach to the point, if such a 
particle, one unit in quantity, were brought up to or were situated 
at that point. It is numerically equal to the number of ergs of 
work which must be done to bring a positive unit of electricity 
from a region where there is absolutely no electric force up to the 
point in question. (Daniell.) Two suppositions are included in 
this. The region where there is an electric force has to be and only 
can be at an infinite distance from all electrified bodies. The 
moving of the particle must take place without any effect upon the 
distribution of electricity on other particles. 

Potential, Constant. Unchanging potential or potential dif- 
ference. 

The ordinary system of incandescent lighting is a constant poten- 
tial svstem, an unvarying potential difference being maintained 
between the two leads, and the current varying according to 
requirements. 

Potential Difference, Electric. If of any two points the 
absolute potentials are determined, the difference between such two 
expresses the potential difference. Numerically it expresses the 
quantity of work which must be done to remove a unit of electric- 
ity from one to the other against electric repulsion, or the energy 
which would be accumulated in moving it the oth^r way. 

A positively charged particle is driven towards the point of lower 
potential. A negatively charged body is driven in the reverse 
direction. 

Potential Difference, Electro= motive. A difference of poten- 
tial in a circuit, or in part of a circuit, which difference produces or 
is capable of producing a current, or is due to the now of such 
current. 

It may be expressed as the fall in potential or the electro-motive 
force included between any two points on a circuit. The current 
in an active circuit is due to the total electro-motive force in the 
circuit. This is distributed through the circuit in proportion to 
the resistance of its parts. Owing to the distribution of electro-motive 
force throughout a circuit including the generator, the terminals of a 
generator on closed circuit may show a difference of potential far 
lower than the electro-motive force of the generator on closed 
circuit. Hence potential difference in such a case has been termed 
available electro-motive force. 

Potential, Electric Absolute. The mathematical expression of 
a property cf a point in space, measuring the tendency which 
existing electric forces would have to drive an electrified unit par- 
ticle away from or prevent its approach to the point in question, 



43° 



STANDARD ELECTRICAL DICTIONARY. 



according to whether the point was situated at or was at a distance 
from the point in question. 

Potential is not the power of doing work, although, as it is 
expressed always with reference to a unit body, it is numerically 
equal to the number of ergs of work which must be done in order 
to bring a positive unit of electricity from a region where there is 
no electric force — which is a region at an infinite 
distance from all electrified bodies — up to the 
point in question. This includes the assump- 
tion that there is no alteration in the general 
distribution of electricity on neighboring bodies. 
(Daniell.) 

In practice the earth is arbitrarily taken as of 
zero electric potential. 

Potential, Fall of. The change in potential 
between any two points on an active circuit. 
The change in potential due to the maintenance 
of a current through a conductor. 

The fall in potential multiplied by the current 
gives work or energy units. 

The fall of potential in a circuit and its subse- 
quent raising by the action of the generator is 
illustrated by the diagram of a helix. In it 
the potential fall in the outer circuit is shown 
by the descent of the helix. This represents 
at once the outer circuit and the fall of potential 
in it. The vertical axis represents the portion 
of the circuit within the battery or generator in 
which the potential by the action of the genera- 
tor is again raised to its original height. 

In a circuit of even resistance the potential 
falls evenly throughout it. 

A mechanical illustration of the relation of 
fall of potential to current is shown in the cut 
| Fig. 269. A vertical wire is supposed to be 
; fixed at its upper end and a lever arm and 
! cord at its lower end, with weight and pulley 
Fig. 269. Mechanical imparts a torsional strain to it. The dials and 
Illustration of Fall i n( } exes show a uniform twisting corresponding 
of Potential and Cur- - „ r ■ . - _, , ° •, r t i£ 

rent Strength. to fall of potential. For each unit of length 

there is a definite loss of twisting, corresponding 
to fall of potential in a unit of length of a conductor of uniform 
resistance. The total twisting represents the total potential differ- 
ence. The weight sustained by the twisting represents the current 
maintained by the potential difference. For a shorter wire less 




STANDARD ELECTRICAL DICTIONARY. 



43i 



twisting would be needed to sustain the weight, as in a shorter 
piece of the conductor less potential difference would be needed to 
maintain the same current. 




Fig. 270. Illustration of the Fall and Redevelopment op Potential in an 
Electric Circuit. 

The fall of potential in a circuit in portions of it is proportional 
to the resistance of the portions in question. This is shown in the 
diagram. The narrow lines indicate high and the broad lines low 
resistance. The fall in different portions is shown as proportional 
to the resistance of each portion. 





■SSH £-^l 


















-<^-«. 


:=> 








°f 










^x 


<^V 




n+ en *4 












\Sr^<^v 




TerUAe 














*^flz°~>^ 




















LcnyCJf. afa.pert 


*■ 




C,r< u 


it dirutcsl ITlsCo qu-l <rrcr.. 





Fig. 271. Diagram of Fall of Potential in a Conductor of Uneven 
Resistance. 

Potential, Magnetic. The magnetic potential at any point of 
a magnetic field expresses the work which would be done by the 
magnetic forces of the field on a positive unit of magnetism as it 
moves from that point to an infinite distance therefrom. The con- 
verse applies to a negative unit. 

It is the exact analogue of absolute electric potential. 

The potential at any point due to a positive pole ;;/ at a distance 



432 STANDARD ELECTRICAL DICTIONARY. 

r is tnjr ; that due to a negative pole — m at a distance r f is equal 

to — m\r f ; that due to both is equal to mjr — m\r f or ml — —\ 

\ r r f J 
Like electric potential .and potential in general, magnetic po- 
tential while numerically expressing work or energy is neither, 
although often defined as such. 

Potential, Negative. The reverse of positive potential. (See 
Potential, Positive.) 

Potential, Positive. In general the higher potential. Taking 
the assumed direction of lines of force, they are assumed to be 
directed or to move from regions of positive to regions of negative 
potential. The copper or carbon plate of a voltaic battery is at 
positive potential compared to the zinc plate. 

Potential, Unit of Electric. The arbitrary or conventional 
potential — or briefly, the potential of a point in an electric field of 
force— is, numerically, the number of ergs of work necessary to 
bring a unit of electricity up to the point in question from a region 
of nominal zero potential — i. e. y from the surface of the earth. 
(Daniell.) This would give the erg as the unit of potential. 

Potential, Zero. The potential of the earth is arbitrarily taken 
as the zero of electric potential. 

The theoretical zero is the potential of a point infinitely distant 
from all electrified bodies. 

Potentiometer. An arrangement somewhat similar to the 
Wheatstone Bridge for determining potential difference, or the 
electro-motive force of a battery. In general principle connection 
is made so that the cell under trial would send a current in one 
direction through the galvanometer. Another battery is connected, 

TiGrg6 

n c 

X T 2 5 4r 5^6 78 9 19 




Fig. 272. Diagram of Potentiometer Connections. 

and in shunt with its circuit the battery under trial and its galvan- 
ometer are connected, but so that its current is in opposition. By 
a graduated wire, like that of a meter bridge, the potential of the 



STANDARD ELECTRICAL DICTIONARY. 433 

main battery shunt can be varied until no current passes. This 
gives the outline of the method only. 

In the cut A B is the graduated potentiometer wire through 
which a current is passed in the direction of the arrow. E is the 
battery under trial, placed in opposition to the other current, with 
a galvanometer next it. Under the conditions shown, if the 
galvanometer showed no deflection, the E. M. F. of the battery 
would be to the E. M. F. between the ends of the potentiometer 
wire, 1 10, as i>^ the distance between the points of con- 
nection, A and D of the battery circuit, is to 10, the full length of 
the potentiometer wire. 

Poundal. The British unit of force ; the force which acting on 
a mass of one pound for one second produces an acceleration of 
one foot. 

Power. Activity ; the rate of activity, of doing work, or of 
expending energy. The practical unit of electric power is the 
volt-ampere or watt, equal to io 7 ergs per second. The kilowatt, 
one thousand watts or volt-amperes, is a frequently adopted unit. 

Power, Electric. As energy is the capacity for doing work, 
electric energy is represented by electricity in motion against a 
resistance. This possesses a species of inertia, which gives it a 
species of kinetic energy. To produce such motion, electro-motive 
force is required. The product of E. M. F. by quantity is therefore 
electric energy. (See Energy, Electric.) 

Generally the rate of energy or power is used. Its dimensions 
are M 5 L 5 /T (intensity or current rate) X M*L 5 /T 2 (electro-motive 
force or potential) =ML 2 /T ; \ which are the dimensions of rate of 
work or activity. The practical unit of electric rate of energy or 
activity is the volt-ampere or watt. By Ohm's law, q. v., we have 
C = E\R ( C = current ; E = potential difference or electro-motive 
force; R = resistance.) The watt by definition = CE. By sub- 
stitution from Ohm's formula we deduce for it the following values : 
C 2 R and E 2 jR. From these three expressions the relations of 
electric energy to E.M.F., Resistance, and Current can be deduced. 

Power of Periodic Current. The rate of energy in a circuit carry- 
ing a periodic current. In such a circuit the electro-motive force 
travels in advance of the current it produces on the circuit. Con- 
sequently at phases or intervals where, owing to the alternations of 
the current, the current is at zero, the electro-motive force may be 
quite high. At any time the energy rate is the product of the 
electro-rnotive force by the amperage. To obtain the power or 
average rate of energy, the product of the maximum electro-motive 
force and maximum current must be divided by two and multiplied 
by the cosine of the angle of lag, which is the angle expressing 
the difference of phase. 



434 



STANDARD ELECTRICAL DICTIONARY. 



Pressel. A press-button often contained in a pear-shaped handle, 
arranged for attachment to the end of a flexible conductor, so as to 
hang thereby. By pressing the button a bell may be rung, or a 
distant lamp may be lighted. 

Pressure, Force or stress exerted directly against any surface. 
Its dimensions are force/area or ML/T 2 -=- h 2 = M/LT 2 . 

Pressure, Electric. Electro-motive force or potential differ- 
ence ; voltage. An expression of metaphorical nature, as the term 
is not accurate. 

Pressure, Electrification by. A crystal of Iceland spar (cal- 
cium carbonate) pressed between the fingers becomes positively 
electrified and remains so for some time. Other minerals act in a 
similar way. Dissimilar substances pressed together and suddenly 
separated carry off opposite charges. This is really contact action, 
not pressure action. 

Primary. A term used to designate the inducing coil in an 
induction coil or transformer ; it is probably an abbreviation for 
primary coil. 

Primary Battery. A voltaic cell or battery generating electric 
energy by direct consumption of material, and not regenerated by 
an electrolytic process. 

The ordinary voltaic cell or galvanic battery is a primary battery. 

Prime, vb. To impart the first charge to one of the armatures 
of a Holtz or other influence machine. 




Fig. 273. 

Prime Conductor, 



Prime Conductor and Proof Plane. 

A metal or metal coated sphere or cylinder 



STANDARD ELECTRICAL DICTIONARY. 



435 



or other solid with rounded ends mounted on insulating supports 
and used to Collect electricity as generated by a frictional electric 
machine. 

According to whether the prime conductor or the cushions are 
grounded positive or negative electricity is taken from the un- 
grounded part. Generally the cushions are grounded, and the prime 
conductor yields positive electricity. 

Probe, Electric. A surgeon's probe, designed to indicate by 
the closing of an electric circuit the presence of a bullet or metallic 
body in the body of a patient. 

Two insulated wires are carried to the end where their ends are 
exposed, still insulated from each other. In probing a wound for 
a bullet if the two ends touch it the circuit is closed and a bell 
rings. If a bone is touched no such effect is produced. The wires 
are in circuit with an electric bell and battery. 

Projecting Power of a Magnet. The power of projecting its 
lines of force straight out from the poles. This is really a matter 
of magnetic power, rather than of shape of the magnet. In electro- 
magnets the custom was followed by making them long to get this 
effect. Such length was really useful in the regard of getting 
room for a sufficient number of ampere turns. 

Prony Brake. A device for measuring the power applied to a 
rotating shaft. It consists of a clamping device to be applied more 




Fig. 274. Prony Brake. 

or less rigidly to the shaft or to a pulley upon it. To the clamp 
is attached a lever carrying a weight. The cut shows a simple 



436 STANDARD ELECTRICAL DICTIONARY. 

arrangement, the shaft A carries a pulley B to which the clamp 
B 1 B 2 is applied. The nuts C 1 C 2 are used for adjustment. A 
weight is placed in the pan E attached to the end of the lever D. 
The weight and clamp are so adjusted that the lever shall stand 
horizontally as shown by the index E. If we call r the radius of the 
pulley and F the friction between its surface and the clamp, it is 
evident that r E y the moment of resistance to the motion of the 
pulley, is equal to the weight multiplied by its lever arm or to 
W R, where IV indicates the weight and R the distance of its 
point of application from the centre of the pulley or r F = R IV. 
The work represented by this friction is equal to the distance 
traveled by the surface of the wheel multiplied by the frictional 
resistance, or is 2 it r n E, in which n is the number of turns 
per minute. But this is equal to 2 it n R IV. These data being 
known, the power is directly calculated therefrom in terms of 
weight and feet per minute. 

Proof =plane. A small conductor, usually disc shaped, carried 
at the end of an insulating handle. It is used to collect electricity 
by contact, from objects electrostatically charged. The charge it 
has received is then measured (see Torsion Balance) or otherwise 
tested. (See Prime Conductor .) 

Proof =sphere. A small sphere, coated with gold-leaf or other 
conductor, and mounted on an insulated handle. It is used instead 
of a proof-plane, for testing bodies whose curvature is small. 




Fig. 275. Box Bridge. 

Proportionate Arms. In general terms the arms of a Wheat- 
stone bridge whose proportion has to be known to complete the 



STANDARD ELECTRICAL DICTIONARY. 437 

measurement. There is a different system of naming them. Some 
designate by this title the two arms in parallel with each other 
branching at and running from one end of the bridge to the two 
galvanometer connections. In the cut of the Box Bridge, A Cand 
A B are the proportionate arms. The third arm is then termed the 
Rheostat arm. (Stewart & Gee.) 

Others treat as proportionate arms the two side members of the 
bridge in parallel with the unknown resistance and third or rheo- 
stat arm. 

Synonym — Ratio Arms. 

Prostration, Electric. Too great exposure to the voltaic arc in 
its more powerful forms causes symptoms resembling those of sun- 
stroke. The skin is sometimes affected to such a degree as to 
come off after a few days. The throat, forehead and face suffer 
pains and the eyes are irritated. These effects only follow expos- 
ure to very intense sources of light, or for very long times. 

Protector, Comb. A lightning arrester, q. v., comprising two 
toothed plates nearly touching each other. 

Protector, Electric. A protective device for guarding the human 
body against destructive or injurious electric shocks. In one 
system, Delany's, the wrists and ankles are encircled by conducting 
bands which by wires running along the arms, back and legs are 
connected. A discharge it is assumed received by the hands will 
thus be short circuited around the body and its vital organs. India 
rubber gloves and shoe soles have also been suggested ; the gloves 
are still used to some extent. 

Pull. A switch for closing a circuit when pulled. It is used 
instead of a push button, q. v., in exposed situations, as its contacts 
are better protected than those of the ordinary push button. 

Pump, Geissler. A form of mercurial air pump. It is used 
for exhausting Geissler tubes, incandescent lamp bulbs and similar 
purposes. 

Referring to the cut, A is a reservoir of mercury with flexible 
tube C connected to a tube at its bottom, and raised and lowered 
by a windlass b, the cord from which passes over a pulley a. When 
raised the mercury tends to enter the chamber B, through the tube 
T. An arrangement of stopcocks surmounts this chamber, which 
arrangement is shown on a larger scale in the three figures X, Y 
and Z. To fill the bulb B, the cocks are set in the position Z ; n 
is a two way cock and while it permits the escape of air below, it 
cuts off the tube, rising vertically from it. This tube, d in the full 
figure connects with a vessel o, pressure gauge p, and tube c, the 
latter connecting with the object to be exhausted. The bulb B 
being filled, the cock m is closed, giving the position Y and the 



43^ 



STANDARD KT^BCTRICAIv DICXIONAP.Y. 



vessel A is lowered until it is over 30 inches below B. This 
establishes a Torricellian vacuum in B. The cock n is now 
turned, giving the position X y when air is at once exhausted 




Fig. 276. Geissler Air Pump. 

from the vessel connected to C. This process is repeated until full 
exhaustion is obtained. In practice the first exhaustion is often 



STANDARD ELECTRICAL DICTIONARY. 



439 



effected by a mechanical pump. By closing the cock on the outlet 
tube c but little air need ever find its way to the chambers o and B. 

Pumping. In incandescent lamps a periodical recurring change 
in intensity due to bad running of the dynamos, or in arc lamps to 
bad feeding of the carbons. 





Fig. 277. Sprengel Air Pump. 
Pump, Sprengel. A form of mercurial air pump. A simple 
form is shown in the cut. Mercury is caused to flow from the 



440 



STANDARD ELECTRICAL DICTIONARY. 



funnel A, through c d to a vessel B. A side connection x leads 
to the vessel R to be exhausted. As the mercury passes x it breaks 
into short columns, and carries air down between them, in this way 
exhausting the vessel R. In practice it is more complicated. It is 
said to give a better vacuum than the Sprengel pump, but to be 
slower in action. 



Pump, Swinburne. 




Fig. 278. 
Swinburne's Air Pump. 



A form of mechanical air pump for 
exhausting incandescent lamp bulbs. 
Referring to the cut, A is a bulb on the 
upper part of a tube G ; above A are 
two other bulbs C and D. From the 
upper end a tube runs to the bulb E. 
Through the cock L> and tube F con- 
nection is made with a mechanical air- 
pump. The tube H leads to a drying 
chamber 7, and by the tube J connects 
with the lamp bulbs or other objects to be 
exhausted. The tube G enters the bottle 
B through an airtight stopper, through 
which a second tube with stopcock K 
passes. In use a vacuum is produced 
by the mechanical pumps, exhausting 
the lamp bulbs to a half inch and draw- 
ing up the mercury in G. The bent 
neck in the bulb E, acts with the bulb 
as a trap to exclude mercury from F. 
When the mechanical pumps have pro- 
duced a vacuum equal to one half inch 
of mercury, the cock L is closed andA^ 
is opened, and air at high pressure 
enters. This forces the mercury up to 
the vessel Z?, half filling it. The high 
pressure is now removed and the mer- 
cury descends. The valve in D closes 
it as the mercury falls to the level G. 
Further air from the lamps enters A y 
and by repetition of the ascent of the 
mercury, is expelled, through D. The 
mercury is again lowered, producing a 
further exhaustion, and the process is 
repeated as often as necessary. 



Push=button. A switch for closing a circuit by means of pressure 
applied to a button. The button is provided with a spring, so that 
when pushed in and released it springs back. Thus the circuit is 
closed only as long as the button is pressed. The electric connec- 
tion may be made by pressing together two flat springs, each con- 



STANDARD ELECTRICAL DICTIONARY. 441 

nected to one of the wires, or by the stem of the button going 
between two springs, not in contact, forcing them a little apart to 
secure good contact, and thereby bridging over the space between 
them. 

Pyro=electricity . A phemenon by which certain minerals when 
warmed acquire electrical properties. (Ganot.) The mineral tour- 
maline exhibits it strongly. It was originally observed in this 
mineral which was found to first attract and then to repel hot ashes. 

The phemenon lasts while any change of temperature within 
certain limits is taking place. In the case of tourmaline the range 
is from about io° C. (50 F.) to 150 C. (302 F.) Above or below 
this range it shows no electrification. 

The effect of a changing of temperature is to develop poles, one 
positive and the other negative. As the temperature rises one end 
is positive and the other negative ; as the temperature becomes 
constant the polarity disappears ; as the temperature falls the poles 
are reversed. 

If a piece of tourmaline excited by pyro-electricity is broken, its 
broken ends develop new poles exactly like a magnet when broken. 

The following minerals are pyro-electric : Boracite, topaz, preh- 
nite, zinc silicate, scolezite, axenite. The following compound 
substances are also so : Cane sugar, sodium-ammonium racemate 
and potassium tartrate. 

The list might be greatly extended. 

The phenomenon can be illustrated by sifting through a cotton 
sieve upon the excited crystal, a mixture of red lead and flowers of 
sulphur. By the friction of the sifting these become oppositely 
electrified ; the sulphur adheres to the positively electrified end, 
and the red lead to the negatively electrified end. (See Analogous 
Pole — A n tilogo us Pole. ) 

Pyromagnetic Motor. A motor driven by the alternation of 
attraction and release of an armature or other moving part, as such 
part or a section of it is rendered more or less paramagnetic by heat. 

Thus imagine a cylinder of nickel at the end of a suspension rod, 
so mounted that it can swing like a pendulum. A magnet pole is 
placed to one side to which it is attracted. A flame is placed so as 
to heat it when in contact with the magnet pole. This destroys 
its paramagnetism and it swings away from the magnet and out of 
the flame. It cools, becomes paramagnetic, and as it swings back 
is reattracted, to be again released as it gets hot enough. This 
constitutes a simple motor. 

A rotary motor ma}- be made on the same lines. Nickel is par- 
ticularly available as losing its paramagnetic property easily. 



442 



STANDARD ELECTRICAL DICTIONARY. 




Fiff. 279. 
Edison's Pyromagnetic Motor. 



Various motors have been constructed on this principle, but none 
have attained any practical importance. Owing to the low temper- 
,^ ature at which it loses its paramag- 

netic properties nickel is the best 
metal for paramagnetic motors. 

In Edison's motor, between the 
pole pieces of an electro-magnet a 
cylinder made up of a bundle of 
nickel tubes is mounted, so as to be 
free to rotate. A screen is placed 
so as to close or obstruct the tubes 
farthest from the poles. On pass- 
ing hot air or products of combus- 
tion of a fire or gas flame through 
the tubes, the unscreened ones are 
heated most and lose their para- 
magnetism. The screened tubes 
are then attracted and the armature 
rotates, bringing other tubes under 
the screen, which is stationary. 
Then the attracted tubes are heated 
while the others cool, and a continuous rotation is the result. 

Pyromagnetic Generator. A current generator producing elec- 
tric energy directly from thermal energy by pyromagnetism. 

Edison's pyromagnetic generator has eight electro-magnets, 
lying on eight radii of a circle, their poles facing inward and their 
yokes vertical. Only two are shown in the cut. On a horizontal 
iron disc are mounted eight vertical rolls of corrugated nickel repre- 
senting armatures. On each armature a coil of wire, insulated 
from the nickel by asbestus is wound. The coils are all in series, 
and have eight connections with a commutator as in a drum 
armature. There are two main divisions to the commutator. Each 
connects with an insulated collecting ring, and the commutator and 
collecting rings are mounted on a spindle rotated by power. 
Below the circle of vertical coils is a horizontal screen, mounted on 
the spindle and rotating with it. 

A source of heat, or a coal stove is directly below the machine 
and its hot products of combustion pass up through the coils, some 
of which are screened by the rotating screen. The effect is that the 
coils are subjected to induction owing to the change in permea- 
bility of the nickel cores, according as they are heated, or as they 
cool when the screen is interposed. The two commutator seg- 
ments are in constant relation to the screen, and current is collected 
therefrom and by the collecting rings is taken to the outside cir- 
cuit. 



STANDARD ELECTRICAL DICTIONARY. 



443 



Pyromagnetistn. The development of new magnetic properties 
or alteration of magnetic sensibility in a body by heat. Nickel and 
iron are much affected as regards their paramagnetic power by rise 
of temperature. 




wr- 



Pyromagnetic Generator. 



Pyrometer, Siemens' Electric. An instrument for measuring 
high temperatures by the variations in electric resistance in a 
platinum wire exposed to the heat which is to be measured. 

Q. Symbol for electric quantity. 

Quad, (a) A contraction for quadrant, used as the unit of 
inductance ; the henry. 

(b) A contraction for quadruplex in telegraphy. 

Quadrant. A length equal to an approximate earth quadrant, 



444 STANDARD ELECTRICAL DICTIONARY. 

equal to io 9 centimeters. It has been used as the name for the 
unit of inductance, the henry, q. v. 
Synonym — Standard Quadrant. 

Quadrant, Legal. The accepted length of the quadrant of the 
earth, 9,978 X io 5 , instead of 10,000 X io 5 (= io 9 ) centimeters ; or 
to 9,978 kilometers instead of 10,000 kilometers. 

Quadrature. Waves or periodic motions the angle of lag of 
one of which, with reference to one in advance of it, is 90 , are 
said to be in quadrature with each other. 

Qualitative. Involving the determination only of the presence 
or absence of a substance or condition, without regard to quantity. 
Thus a compass held near a wire might determine qualitatively 
whether a current was passing through the wire, but would not be 
sufficient to determine its quantity. (See Quantitative.) 

Quality of Sound. The distinguishing characteristic of a sound 
other than its pitch ; the timbre. 

It is due to the presence with the main or fundamental sound of 
other minor sounds called overtones, the fundamental note pre- 
vailing and the other ones being superimposed upon it. The 
human voice is very rich in overtones ; the telephone reproduces 
these, thus giving the personal peculiarities of every voice. 

Synonym — Timbre. 

Quantitative. Involving the determination of quantities. Thus 
a simple test would indicate that a current was passing through a 
wire. This would be a qualitative test. If by proper apparatus 
the exact intensity of the current was determined, it would be a 
quantitative determination. (See Qualitative.) 

Quantity. This term is used to express arrangements of elec- 
trical connections for giving the largest quantity of current, as a 
quantity armature, meaning one wound for low resistance. 

A battery is connected in quantity when the cells are all in par- 
allel. It is the arrangement giving the largest current through a 
very small external resistance. 

The term is now virtually obsolete (Daniell) ; " in surface," " in 
parallel," or " in multiple arc " is used. 

Quantity, Electric. Electricity may be measured as if it were 
a compressible gas, by determining the potential it produces when 
stored in a defined recipient. In this way the conception of a 
species of quantity is reached. It is also measured as the quantity 
of current passed by a conductor. 

Thus a body whose surface is more or less highly charged with 
electricity, is said to hold a greater or less quantity of electricity. 



STANDARD ELECTRICAL DICTIONARY. 445 

It may be defined in electrostatic or electro-magnetic terms. 
(See Quantity, Electrostatic — Quantity, Electro=magnetic.) 

Quantity, Electro=magnetic. Quantity is determined electro- 
magnetically by the measurement of current intensity for a second 
of time : its dimensions are therefore given by multiplying inten- 
tity or current strength by time. The dimensions of intensity are 
M* Iy 5 /T ; therefore the dimensions of electro-magnetic quantity 
are M* I^/T xT = M^ Li 

Quantity, Electro=magnetic, Practical Unit of. The quantity 
of electricity passed by a unit current in unit time ; the quantity 
passed by one ampere in one second ; the coulomb. 

It is equal to 3 X io 9 electrostatic absolute units of quantity and 
to 1-10 of the electro-magnetic absolute unit of quantity. 
One coulomb is represented by the deposit of 

.00,111,815 gram, or .017,253 grain of silver, 
,00,032,959 gram, or .005,804 grain of copper, 
.0,003,392 gram, or .005,232 grain of zinc. 
If water is decomposed by a current each coulomb is represented 
by the cubic centimeters of the mixed gases (hydrogen and oxy- 
gen) given by the following formula. 

0.1738 x 76(2 73 +C°) 
h X 273 
in which C° is the temperature of the mixed gases in degree 
centigrade and h is the pressure in centimeters of mercury column; 
or by 0.01058 X 3° (49 1 + F° — 32) 

h X 49 1 
for degrees Fahrenheit and inches of barometer. 

Quantity, Electrostatic. Quantity is determined electro- 
statically by the repulsion a charge of given quantity exercises 
upon an identical charge at a known distance. The force evidently 
varies with the product of the two quantities, and by the law of 
radiant forces also inversely with the square of the distance. The 
dimensions given by these considerations is Q X Q/L 2 . This is 
the force of repulsion. The dimensions of a force are ML/T 2 . 
Equating these two expressions we have : 

Q 2 /L 2 = ML/T 2 or Q = M*L*/T, which are the dimensions of 
electrostatic quantity. 

Quantity, Meter. An electric meter for determining the quan- 
tity of electricity which passes through it, expressible in coulombs 
or ampere hours. All commercial meters are quantity meters. 

Quartz. A mineral, silica, SiO._>. It has recently been used by 



446 STANDARD ELECTRICAL DICTIONARY. 

C. V. Boys and since by others in the making of filaments for 
torsion suspensions. The mineral is melted, while attached to an 
arrow or other projectile. It is touched to another piece of quartz 
or some substance to which it adheres and the arrow is fired off 
from the bow. A very fine filament of surpassingly good qualities 
for galvanometer suspension filaments is produced. 

As a dielectric it is remarkable in possessing but one-ninth the 
residual capacity of glass. 

Quicking. The amalgamating of a surface of a metallic object 
before silver plating. It secures better adhesion of the deposit. It 
is executed by dipping the article into a solution of a salt of mer- 
cury. A solution of mercuric nitrate i part, in water ioo parts, 
both by weight, is used. 

R. (a) Abbreviation and symbol for Reamur, as io° R., mean- 
ing io° by the Reamur thermometer. (See Reamur Scale.) 

(b) Symbol for resistance, as in the expression of Ohm's Law 
C=E\R. 

p. (Greek r) Symbol for specific resistance. 

Racing of Motors. The rapid acceleration of speed of a motor 
when the load upon it is removed. It is quickly checked by 
counter-electro-motive force. (See Motor, Electric.) 

Radian. The angle whose arc is equal in length to the radius ; 
the unit angle. 

Radiant Energy. Energy, generally existing in the luminifer- 
ous ether, kinetic and exercised in wave transmission, and ren- 
dered sensible by conversion of its energy into some other form 
of energy, such as thermal energy. 

If the ether waves are sufficiently short and not too short, they 
directly affect the optic nerve and are known as light waves ; they 
may be so short as to be inappreciable by the eye, yet possess the 
power of determining chemical change, when they are known as 
actinic waves ; they may be also so long as to be inappreciable by 
the eye, when they may be heat-producing waves, or obscure 
waves. 

Other forms of energy may be radiant, as sound energy dispersed 
by the air, and gravitational energy, whose connection with the 
ether has not yet been demonstrated. 

Radiation. The traveling or motion of ether waves through 
space. 

Radicals. A portion of a molecule , possessing a free bond and 
hence free to combine directly. A radical never can exist alone, 
but is only hypothetical. An atom is a simple radical, an unsatur- 
ated group of atoms is a compound radical. 



STANDARD ELECTRICAL DICTIONARY. 447 

Radiometer. An instrument consisting of four vanes poised 
on an axis so as to be free to rotate, and contained in a sealed glass 
vessel almost perfectly exhausted. The vanes of mica are black- 
ened on one side. 

On exposure to light or a source of heat (ether waves) the vanes 
rotate. The rotation is due to the beating back and forth of air 
molecules from the surface of the vanes to the inner surface of the 
glass globe. 

Radiometer, Electric. A radiometer in which the motion of 
the molecules of air necessary for rotation of the vane is produced 
by electrification and not by heating. 

Radio=micrometer. iVn instrument for detecting radiant energy 
of heat or light form. It consists of a minute thermopile with its 
terminals connected by a wire, the whole suspended between the 
poles of a magnet. A" minute quantity of heat produces a current 
in the thermopile circuit, which, reacted on by the field, produces 
a deflection. A convex mirror reflecting light is attached so as to 
move with the thermopile. The instrument is of extraordinary 
sensitiveness. It responds to ^wuhooo °f a degree Centigrade or 
about roowoo degree Fahrenheit. 

Radiophony. The production of sound by intermittent action 
of a beam of light upon a body. With possibly a few exceptions 
all matter may produce sound by radiophony. 

Range Finder. An apparatus for use on shipboard to determine 
the distance of another ship or object. It is designed for ships of 
w T ar, to give the range of fire, so as to set the guns at the proper 
elevation. The general principle involved is the use of the length 
of the ship if possible, if not of its width, as a base line. Two tele- 
scopes are trained upon the object and kept trained continuously 
thereon. The following describes the Fiske range finder. 

The range finder comprises two fairly powerful telescopes, each 
mounted on a standard, which can be rotated round a vertical axis, 
corresponding with the center of the large disc shown in the 
engraving. One-half of the edge of this disc is graduated to 90 
on either side of a zero point, and below the graduation is fixed a 
length of platinum silver w T ire. This wire only extends to a dis- 
tance of 81. i° on either side of zero, and is intended to form two 
arms of a Wheatstone bridge. The sliding contact is carried by the 
same arm as the telescope standards, so that it moves with the tele- 
scope. The two instruments are mounted at a known distance 
apart on the ship, as shown diagrammatically in the cut. Here A 
and B are the centers of the two discs, C and D the arms carrying 
the telescopes, and E and F the platinum silver wires. Suppose 
the object is at T, such that A B Tis aright angle, then AT=AB/ 
sin A TB. 



448 



STANDARD ELECTRICAL DICTIONARY. 



If the two sectors are coupled up as shown, with a battery, h, 
and a galvanometer, by the wires, a b and c d, then since the arm, 
£, on being aligned on the object takes the position c 1 while d 
remains at zero, the Wheats tone bridge formed by these segments 
and their connections will be out of balance, and a current will 
flow through the galvanometer, which may be so graduated as to 
give the range by direct reading, since; the current through it will 

A 




[Fig. 281. Range Finder. 
increase with the angle AT B. In general, however, the angle 
A B T 4 will not be a right angle, but some other angle cp. In this 
case A T= A B/sin A T B X sin A B T, and hence it will only be 
necessary to multiply the range reading on the galvanometer by 
the sine of the angle A B T, which can be read directly by the 
observer at B. This multiplication is not difficult, but by suitably 
arranging his electrical appliances Lieutenant Fiske has succeeded 
in getting rid of it, so that the reading of the galvanometer always 
gives the range by direct reading, no matter what the angle at B 
may be. To explain this, consider the two telescopes shown in 
the cut in the positions C and D ; the whole current then has a 



STANDARD ELECTRICAL DICTIONARY. 



449 



certain resistance. Next suppose them, still remaining parallel, 
in the positions O and D x . The total resistance of the circuit is 
now less than before, and hence if C 1 , one of the telescopes, is 
moved out of parallel to the other, through a certain angle, the 
current through the galvanometer will be greater than if it were 
moved through an equal angle out of a parallel when the telescopes 
were in the positions CandZA The range indicated is, therefore, 
decreased, and by properly proportioning the various parts it is 
found that the range can always be read direct from the galvanom- 
eter, or in other words the multiplication of A B sin A T B by sin 
A B T is to all intents and purposes performed automatically. 
There is, it is true, a slight theoretical error ; but by using a small 
storage battery and making the contents carefully it is said to be 
inappreciable. Each telescope is fitted with a telephone receiver 
and transmitter, so that both observers can without difficulty decide 
on what point to align their telescopes. It will be seen that it is 
necessary that the lines of sight of two telescopes should be parallel 
when the galvanometer indicates no current. It has been proposed 
to accomplish this by sighting both telescopes on a star near the 
horizon, which being practically an infinite distance away insures 
the parallelism of the lines of sight. 

Rate Governor. An apparatus for securing a fixed rate of 
vibration of a vibrating reed. It is applied in simultaneous teleg- 
raphy and telephoning over one wire. The principle is that of 
the regular make and break mechanism, with the feature that the 
contact is maintained during exactly one-half of the swing of the 
reed. The contact exists during the farthest half of the swing of 
the reed away from the attracting pole. 




C26 \\CZZc r^c 



Fig-. 282. Langdon Davies' Rate Governor. 

In the left hand figure of the cut, K is the key for closing the 
circuit. A is the base for attachment of the reed. V is the con- 
tact-spring limited in its play to the right by the screw S. C is 
the actuating magnet. By tracing the movements of the reed, 
shown on an exaggerated scale in the three right hand figures, it 
will be seen that the reed is in electric contact with the spring 



45o 



STANDARD ELECTRICAL DICTIONARY. 




during about one-half its movement. The time of this connection 
is adjustable by the screw S. 
Synonym — Iyangdon Davies' Rate Governor or Phonophone. 

Ray, Electric. Rata torpedo. The torpedo, a fish having the 
same power of giving electric shocks as 
that possessed by the electric eel, q. v. 
(See also Animal Electricity,) 

Reaction of Dynamo, Field and 
Armature. A principle of the dynamo 
current generator, discovered by Soren 
Hjorth of Denmark. 

When the armature is first rotated it 
moves in a field due to the residual 
magnetism of the field magnet core. This 
field is very weak, and a slight current 
only is produced. This passing in part 
or in whole through the field magnet 
cores slightly strengthens the field, whose 
increased strength reacts on the armature 
increasing its current, which again 
strengthens the field. In this way the 
current very soon reaches its full strength 
as due to its speed of rotation. 

The operation is sometimes termed building up. 

Sometimes, when there is but a trace of residual magnetism, it is 
very hard to start a dynamo. 

Reading Telescope. A telescope for reading the deflections of 
a reflecting galvanometer. 

A long horizontal scale is mounted at a distance from the 
galvanometer and directly below or above the centre of the scale a 
telescope is mounted. The telescope is so directed that the mirror 
of the galvanometer is in its field of view, and the relative posi- 
tions of mirror, scale and telescope are such that the image of the 
scale in the galvanometer mirror is seen by the observer looking 
through the telescope. 

Under these conditions it is obvious that the graduation of the 
scale reflected by the mirror corresponds to the deflection of the 
galvanometer needle. 

The scale may be straight or curved, with the galvanometer in 
the latter case, at its centre of curvature. 

Reamur Scale. A thermometer scale in use in some countries 
cf Continental Europe. The temperature of melting ice is o° ; the 
temperature of condensing steam is 8o° ; the degrees are all equal 



Fiff. 283. 
Torpedo or Electric Ray 



STANDARD ELECTRICAL DICTIONARY. 451 

in length. For conversion to centigrade degrees multiply degrees 
Reamur by f . For conversion to Fahrenheit degrees multiply by f 
and add 32 if above o° R., and if below subtract 32. Its symbol 
is R., as io° R. 

Recalescence. A phenomenon occurring during the cooling of 
a mass of steel, when it ' suddenly emits heat and grows more 
luminous for an instant. It is a phase of latent heat, and marks 
apparently the transition from a non-magnetizable to a magnetiz- 
able condition. 

Receiver. In telephony and telegraphy, an instrument for 
receiving a message as distinguished from one used for sending or 
transmitting one. 

Thus the Bell telephone applied to the ear is a receiver, while 
the microphone which is spoken into or against is the transmitter. 

Receiver, Harmonic. A receiver including an electro-magnet 
whose armature is an elastic steel reed, vibrating to a particular 
note. Such a reed responds to a series of impulses succeeding each 
other with the exact frequency of its own natural vibrations, and 
does not respond to any other rapid series of impulses. (See Tele- 
graph Harmonic.) 

Reciprocal. The reciprocal of a number is the quotient obtained 
by dividing one by the number. .Thus the reciprocal of 8 is x /%. 

Applied to fractions the above operation is carried out by simply 
inverting the fraction. Thus the reciprocal of % is % or iy£. 

Record, Telephone. Attempts have been made to produce a 
record from the vibrations of a telephone disc, which could be 
interpreted by phonograph or otherwise. 



Fig. 284. Morse Recorder or Embosser. 

Recorder, Morse. A telegraphic receiving apparatus for record- 



452 STANDARD ELECTRICAL DICTIONARY. 

ing on a strip of paper the dots and lines forming Morse characters 
as received over a telegraph line. Its general features are as follows : 
A riband or strip of paper is drawn over a roller which is slightly 
indented around its centre. A stylus or blunt point carried by a 
vibrating arm nearly touches the paper. The arm normally is 
motionless and makes no mark on the paper. An armature is 
carried by the arm and an electro-magnet faces the armature. When 




Fig. 285. Inking Roller Mechanism of Morse Recorder. 

a current is passed through the magnet the armature is attracted 
and the stylus is forced against the paper, depressing it into the 
groove, thus producing a mark. When the current ceases the 
stylus is drawn back by a spring. 

In some instruments a small inking roller takes the place of the 
stylus, and the roller is smooth. The cut, Fig. 285, shows the plan 
view of the ink-roller mechanism. J is the roller, L is the ink 
well, C 1 is the arm by which it is raised or lowered by the electro- 
magnet, as in the embosser. ►S ,S is the frame of the instrument, 
and B the arbor to which the arm carrying the armature is secured, 
projecting to the right. A spring is arranged to rub against the 
edge of the inking roller and remove the ink from it. 

The paper is fed through the apparatus by clockwork. At the 
present day sound reading has almost entirely replaced the sight 
reading of the recorder. 

Recorder, Siphon. A recording apparatus in which the inked 
marks are made on a strip of paper, the ink being supplied by a 
siphon terminating in a capillary orifice. 

In the cut N S represents the poles of a powerful electro-mag- 
net. A rectangular coil b b of wire is suspended between the coils. 
A stationary iron core a intensifies the field. The suspension wire 
ff 1 has its tension adjusted at h. This wire acts as conductor for 



STANDARD ELECTRICAL DICTIONARY. 



453 



the current. The current is sent in one or the other direction or 
is cut off in practice to produce the desired oscillations of the coil 
b b. A glass siphon n I works upon a vertical axis /. One end / is 
immersed in an ink well m. Its longer end n touches a riband of 
paper o o. The thread k attached to one side of the coil pulls the 
siphon back and forth according to the direction of current going 
through the electro-magnet cores. A spiral spring adjusted by a 




Fig. 



Siphon Recorder. 



hand-screw controls the siphon. In operation the siphon is drawn 
back and forth producing a zigzag line. The upward marks repre- 
sent dots, the downward ones dashes. Thus the Telegraphic Code 
can be transmitted on it. To cause the ink to issue properly, 
electrification by a static machine has been used, when the stylus 
does not actually touch the paper, but the ink is ejected in a series 
of dots. 

Reducteur for Ammeter. A resistance arranged as a shunt to 
diminish the total current passing through an ammeter. It is anal- 
ogous to a galvanometer shunt. (See Multiplying Power of^Shunt. ) 

Reducteur for Voltmeter. A resistance coil connected in series 
with a Voltmeter to diminish the current passing through it. Its 
resistance being known in terms of the resistance of the voltmeter 
it increases the range of the instrument so that its readings may 
cover double or more than double their normal range. 

Reduction of Ores, Electric. Treatment of ores by the electric 
furnace (see Furnace, Electric.) The ore mixed with carbon and 
flux is melted by the combined arc and incandescent effects of the 
current and the metal separates. In another type the metal is 



454 STANDARD ELECTRICAL DICTIONARY. 

brought into a fusible compound which is electrolyzed while fused 
in a crucible. Finally processes in which a solution of a salt of the 
metal is obtained, from which the metal is obtained by electrolysis, 
may be included. Aluminum is the metal to whose extraction the 
first described processes are applied. 

Refraction, Electric Double. Double refraction induced in 
some materials by the action of either an electrostatic, magnetic 
or an electro-magnetic field. 

The intensity or degree of refracting power is proportional to the 
square of the strength of field. 

Refreshing Action. In electro-therapeutics the restoration of 
strength or of nerve force by the use of voltaic alternatives, q. v* 

Region, Extra=polar. In electro-therapeutics the area or region 
of the body remote from the therapeutic electrode. 

Region, Polar. In electro-therapeutics the area or region of 
the body near the therapeutic electrode. 

Register, Electric. There are various kinds of electric registers, 
for registering the movements of watchmen and other service. 
Contact or press buttons may be distributed through a factory. 
Each one is connected so that when the circuit is closed thereby a 
mark is produced by the depression of a pencil upon a sheet or 
disc of paper by electro-magnetic mechanism. The paper is moved 
by clockwork, and is graduated into hours. For each push-button 
a special mark may be made on the paper. The watchman is 
required to press the button at specified times. This indicates his 
movements on the paper, and acts as a time detector to show 
whether he has been attending to his duty. * 

Register, Telegraphic. A term often applied to telegraph 
recorders, instruments for producing on paper the characters of 
the Morse or other alphabet. 

Regulation, Constant Current. The regulation of a dynamo 
so that it shall give a constant current against any resistance in the 
outer circuits, within practical limits. It is carried out in direct 
current machines generally by independent regulators embodying 
a controlling coil with plunger or some equivalent electro-magnetic 
device inserted in the main circuit and necessarily of low resist- 
ance. In some regulators the work of moving the regulator is 
executed mechanically, but under electrical control ; in others the 
entire work is done by the current. 

A typical regulator or governor (Golden's) of the first class com- 
prises two driven friction wheels between which is a driving friction 
wheel, which can engage with one driven wheel only at once. It 
is brought into engagement with one or the other by a solenoid 



STANDARD ELECTRICAL DICTIONARY. 455 

and plunger. As it touches one wheel it turns it in one direction. 
This moves a sliding contact in one direction so as to increase a 
resistance. This corresponds to a motion of the plunger in one 
direction. As the driving wheel moves in the opposite direction 
by a reverse action it diminishes the resistance. Thus the increase 
and decrease of resistance correspond to opposite movements of the 
solenoid plunger, and consequently to opposite variations in the 
current. The whole is so adjusted that the variations in resistance 
maintain a constant amperage. The resistance is in the exciting 
circuit of the dynamo. 

In Brush's regulator, which is purely mechanical, a series 
dynamo is made to give a constant current by introducing across 
the field magnets a shunt of variable resistance, whose resistance 
is changed by an electro-magnet, whose coils are in circuit with 
the main current. Carbon resistance discs are used which the 
electro-magnet by its attraction for its armature, presses with vary- 
ing intensity. This alters the resistance, decreasing it as the cur- 
rent increases and the reverse. As the connection is in shunt this 
action goes to maintain a constant current. 

Regulation, Constant Potential. The regulation of constant 
potential dynamos is executed on the same lines as that of constant 
current dynamos. If done by a controlling coil, it must for con- 
stant potential regulation be wound with fine wire and connected 
as a shunt for some part of the machine. 

Regulation of Dynamos. The regulation of dynamos so that 
they shall maintain a constant potential difference in the leads of 
their circuit for multiple arc systems or shall deliver a constant 
current in series systems. Hence two different systems of regula- 
tion are required, (a) constant potential regulation — (6) constant 
current regulation. The first named is by far the more important, 
as it concerns multiple arc lighting, which is the system univers- 
ally used for incandescent lighting. 

S. P. Thompson thus summarizes the methods of governing or 
regulating dynamos. Premising that alteration of the magnetic 
flux is the almost universal way of control, it can be done in two 
ways; first, by varying the excitation or ampere turns of the field, 
and second by varying the reluctance of the magnetic circuit. 
The excitation or magnetic flux may be varied (a) by hand, with 
the aid of rheostats and commutators in the exciting circuit ; (6) 
automatically, by governors, taking the place of the hand ; (c) by 
compound windings. The magnetic circuit may have its reluc- 
tance caused to vary in several ways ; (d) by moving the pole pieces 
nearer to or further from the armature ; (e) by opening or closing 
some gap in the magnetic circuit (field-magnet core) ; (f) by draw- 
ing the armature endways from between the pole pieces ; (g) by 



456 STANDARD ELECTRICAL DICTIONARY. 

shunting some of the magnetic lines away from the armature by a 
magnetic shunt. The latter magnetic circuit methods d y e,f y and 
g> have never met with much success except on small machines or 
motors. Method e is adopted in the Edison motor, the yoke being 
withdrawn or brought nearer the cores of the coils. (See Regula- 
tion , Constant Current — Regulation, Constant Potential.) 

Reguline. adj. Having the characteristics of a piece of metal, 
being flexible, adherent, continuous, and coherent. Applied to 
electrolytic deposits. 

Relative. Indicating the relation between two or more things 
without reference to absolute value of any one of them. Thus one 
lamp may be of relatively double resistance compared to another, 
but this states nothing of the resistance in ohms of either lamp. 

Relay. A receiving instrument which moves in accordance 
with impulses of currents received, and in so moving opens and 
closes a local circuit, which circuit may include as powerful a bat- 
tery as required or desirable, while the relay may be on the other 
hand so delicate as to work with a very weak current. 




Fig. 287. Relay. 

The typical relay includes an electro-magnet and armature. To 
the latter an arm is attached and the lower end of the arm works in 
pivots. As the armature is attracted the arm swings towards the 
magnet. When the current is cut off, the armature and arm are 
drawn back by a spring. When the arm swings towards the mag- 
net its upper end touching a contact screw closes the local circuit. 
When it swings back it comes in contact with a second screw, 
with insulated point, and opens the circuit as it leaves the first 
named screw. 

One terminal connects with the arm through the pivots and 



STANDARD ELECTRICAL DICTIONARY. 



457 



frame. The other connects with the contact screw through the 
frame carrying it 

Synonym — Relay Magnet. 

Relay Bells. Bells connected by relay connection to a main 
line for acoustic telegraphy. A stroke on one bell indicates a dot and 
on the other a dash. The system is now nearly extinct. 

Relay, Box=sounding. A relay which is surrounded by or 
mounted on a resonator or wooden box of such proportions and 
size as to reinforce the sound. This enables a relay to act as a 
sounder, its weak sounds being virtually magnified so as to be 
audible. 

Relay Connection. A connection used in telegraphy, including 
a local battery, with a short circuit normally open, but closed by a 
switch and a sounder or other appliance. The latter is made very 
sensitive so as to be worked by a feeble current, and is connected 
to the main line. A very slight current closes the switch and the 





Fig. 288. Relay or Local Circuit. 

local battery comes into operation to work a sounder, etc. When 
the current ceases on the main line the switch opens and throws 
the local battery out of action. The switch is termed a relay, q. v. A 
long main line may thus produce strong effects at distant stations, 
the intensity of action depending on the local battery. 

Relay, Differential. A relay containing two coils wound differ- 
entially, and of the same number of turns and resistance. If two 
equal currents pass through the coils they counteract each other and 
no action takes place. If there is a difference in the currents the 
relay acts as one coil preponderates. The coils may be wound for 
uneven currents with different resistance and number of turns. 

Relay, Microphone. A relay connection applied to a telephone 



453 STANDARD ELECTRICAL DICTIONARY. 

circuit. It consists of a microphone mounted in front of the dia- 
phragm of a telephone receiver. In circuit with the microphone 
is a battery and second telephone receiver. The microphone is 
supposed to intensify the sounds of the first telephone. 

Relay, Polarized. A relay whose armature is of steel, and 
polarized or permanently magnetized, or in which a permanent mag- 
net is used as the basis for the electro-magnets. In the relay shown 
in the cut the coils shown are mounted on cores carried on the 
end of a powerful bent permanent magnet. Thus when no current 
passes their upper poles are both of the 
same sign, and the horizontally vibrat- 
ing tongue is held by the magnetic attrac- 
tion against one or the other pole piece. 
If a current is sent through the electro- 
magnet it gives opposite polarity to the 
two polar extensions. As the end of 
the vibrating tongue is of polarity 
determined by the permanent magnet 
it is attracted to one pole and and re- 
pelled from the other. On cessation of 
current it remains attached by the per- 
manent magnetism. If now a current 

„. '" „ is sent in the opposite direction the two 

Fist. 288. Polarized Relay. •, • rL ■ ., _ * • , 

8 poles again acquire opposite polarity, 

the reverse of the former, and the tongue flies across to the oppo- 
site side. On cessation of current it remains attached as before by 
the permanent magnetism. 

In its movements to and fro the relay tongue opens and closes a 
contact, so as to work a sounder or other apparatus. The polar- 
ized relay is of high sensibility, and requires little or no change of 
adjustment. 

Reluctance. In a magnetic circuit or portion thereof, the resist- 
ance offered to the flow of lines of force. The magnetic circuit 
as has already been stated is treated like an electric circuit, and in 
it reluctance occupies the place of resistance in the electric circuit. 
It is the reciprocal of permeance. S. P. Thompson expresses the law 
thus: 

magneto-motive force. 

Total number of magnetic lines = r- i — r~Z 

& magnetic reluctance. 

Synonyms — Magnetic Reluctance — Magnetic Resistance. 

Reluctance, Unit of. The reluctance of a circuit through which 
unit magnetizing power (magneto-motive force) can produce a 
unit of induction or one line of force. This value is very high ; 
the reluctance of ordinary magnetic circuits ranges from io-° to 
10- 8 unit of reluctance. 




STANDARD ELECTRICAL DICTIONARY. 459 

Reluctivity. Specific reluctance ; the reluctance of a cube of 
material whose edge measures one centimeter in length. It is a 
quality bearing the same relation to reluctance that permeability 
does to permeance. 

It is denned as the reciprocal of magnetic permeability. 
(Kenelly.) If plotted as a curve for different values of the mag- 
netizing force it is found to be nearly a straight line, a linear 
function of the magnetizing force, H with the equation a + b H. 
Reluctivity is the property of a substance ; reluctance is the 
property of a circuit. 

Remanence. The residual magnetism left after magnetic induc- 
tion, expressed in lines of force per square centimeter. 

Repeater. In telegraphy an instrument for repeating the signals 
through a second line. It is virtually a relay which is operated by 
the sender, and wmich in turn operates the rest of the main line, 
being situated itself at about the middle point of the distance 
covered. In the simpler forms of repeater two relays are used, one 
for transmission in one direction the other for transmission in the 
other. An attendant switches one or the other in as required. 

Thus a common relay is virtually a repeater for its local circuit. 
If such a relay is placed half way down a line, and if the line 
beyond it is connected as its local, it becomes a repeater. 

Some forms of repeaters are automatic, and repeat both ways 
without the need of an attendant. 

It is the practice to somewhat prolong the signals sent through a 
repeater. 

Replenisher, Sir William Thomson's. A static accumulating 
influence machine contained in Thomson's quadrant electrometer 
and used to change the quadrants. The cut shows the horizontal 
section and construction of the apparatus. 

It contains two gilt brass inductors A B, and two eccentric sectors 
or carriers, C> D, w T hich are mounted on an ebonite spindle, which-is 
spun around by the fingers. The springs s s l connect each with its 
inductor ; the springs kS S 1 connect only each other, and touch the 
sectors as they turn around. 

One of the inductors may be always assumed to be of slightly 
higher potential than that of the other one. When the carriers are 
in contact with the springs .S ►S 1 they are each charged by induc- 
tion with electricity opposite in sign to that of the nearest quad- 
rant. As they leave the springs .5 .S 1 in their rotation, they next 
touch the springs s s l , but of the recently opposite inductor. They 
share each a portion of its charge with the inductors building up 



460 



STANDARD ELECTRICAL DICTIONARY. 



their charges. The action is repeated over and over again as they 
rotate. 

Reservoir, Common. A term applied to the earth, because all 
electrified bodies discharge into it if connected thereto. 




Diagram of Thomson's Replenisher. 



Residual Atmosphere. The air left in a receiver after exhaus- 
tion by an air pump. The quantity, where good air pumps are 
used, is very minute. 

Residue, Electric. The residual charge of a condenser. (See 

Charge ', Residual.) 

Resin, (a) The product obtained by non-destructive distillation 
of the juice of the pitch pine. It is the solid residue left after the 
turpentine has been evaporated or distilled. It is a mixture of 
abietic acid C u H (;4 5 , and pinic acid C 20 H 30 2 . It is an insulator ; 
its specific inductive capacity is 2.55. (Baltzmann.) 

Synonyms — Colophony — Rosin. 

(d) The name is also generally applied to similar substances 
obtained from the sap of other trees ; thus shellac is a resin. The 



STANDARD ELECTRICAL DICTIONARY. 461 

rasins are a family of vegetable products ; the solid portions of the 
sap of certain trees. Common resin, lac, dragons blood, are 
examples. They are all dielectrics and sources of resinous or 
negative electricity when rubbed with cotton, flannel, or silk. (See 
Electrostatic Series. ) 




Fig. 290. Thomson's Replenished 

Resinous Electricity. Negative electricity- ; the electricity pro- 
duced upon the surface of a resinous body by rubbing it ; such a 
body is shellac or sealing wax ; flannel and other substances may 
be used as the rubbing material. (See Electrostatic Series.) 

Resistance, (a) The quality of an electric conductor, in virtue 
of which it opposes the passage of an electric current, causing the 
disappearance of electro-motive force if a current passes through 
it, and converting electric energy into heat energy in the passage 
of a current through it. If a current passes through a conductor 
of uniform resistance there is a uniform fall of potential all along 
its length. If of uneven resistance the fall in potential varies 
with the resistance. (See Potential, Fall of.) 

The fall of potential is thus expressed by Daniell. "In a con- 
ductor, say a wire, along which a current is steadily and uniformly 
passing, there is no internal accumulation of electricity, no density 
of internal distribution ; there is, on the other hand, an unequally 
distributed charge of electricity on the surface of the wire, which 
results in a potential diminishing within the wire from one end 
of the wire to the other." 

Resistance varies inversely with the cross section of a cylindrical 
or prismatic conductor, in general with the average cross-section 



462 STANDARD ELECTRICAL DICTIONARY. 

of any conductor, and in the same sense directly with its true or 
average or virtual length. It varies for different substances, and 
for different conditions as of temperature and pressure for the 
same substance. A rise of temperature in metals increases the 
resistance, in some bad conductors a rise of temperature decreases 
the resistance. 

Approximately, with the exception of iron and mercury, the re- 
sistance of a metallic conductor varies with the absolute tempera- 
ture. This is very roughly approximate. 

Except for resistance energy would not be expended in main- 
taining a current through a circuit. The resistance of a conduc- 
tor may be supposed to have its seat and cause in the jumps from 
molecule to molecule, which the current has to take in going 
through it. If so a current confined to a molecule would, if once 
started, persist because there would be no resistance in a molecule. 
Hence on this theory the Amp£rian currents (see Magnetism, 
Ampkre's Theory of) would require no energy for their mainten- 
ance and Ampere's theory would become a possible truth. 

When metals melt their resistance suddenly increases. 

Light rays falling on some substances, notably selenium, q. v., 
vary the resistance. 

Longitudinal stretching of a conductor decreases it, it increases 
with longitudinal compression, and increases in iron and dimin- 
ishes in tin and zinc when a transverse stress tends to widen the 
conductor. 

(b) The term resistance is used to express any object or conduc- 
tor used in circuit to develop resistance. 

Resistance, Apparent. Impedance ; the virtual resistance of a 
circuit including the spurious resistance due to counter-electro- 
motive force. It may be made up of true resistance and partly of 
an inductive reaction, as it represents the net factor, the entire 
obstruction to the passage of a current, and not merely a super- 
added resistance or counter-electro-motive force. 

Synonym — Impedance. 

Resistance, Assymmetrical. Resistance which varies in 
amount in different directions through a conductor. It implies a 
compound or composite conductor such as the human system. 
The presence of counter-electro-motive force in different parts of 
a conductor may bring about assymmetrical resistance. 

Resistance, B. A. Unit of. The British Association Ohm. (See 
Ohm, B. A.) 

Resistance Box. A box filled with resistance coils. The 
coils are connected in series so that a circuit including any given 



STANDARD ELECTRICAL DICTIONARY. 463 

number has their aggregate resistance added to its own. The 
terminals of consecutive coils are connected to short blocks of 
brass which are secured to the top of the box, lying flatwise upon 
it, nearly but not quite in contact with each other. Plugs of brass 
are supplied which can go in between pairs of blocks, which have 



Fig-. 291. Resistance Box. 

a pair of grooves reamed out to receive them. Such plugs short 
circuit the coil below them when in position. The cut shows 
how such coils are connected and the use of plugs to short circuit 
them. The diagram shows the top of a Wheatstone bridge, q. v., 
resistance box with connections for determining resistances. 

Resistance Box, Sliding. A resistance box whose coils are 
set in a circle. Two metal arms with handles are pivoted at the 
centre of the circle and by moving them around they make and break 
contacts so as to throw the coils in and out of circuit. The object is 
to permit an operator to adjust resistance without looking at the 
box — an essential in duplex telegraphy. 

Resistance, Breguet Unit of. The same in origin as the Dig- 
ney Unit. (See Resistance, Digney Unit of.) 
It is equal to 9.652 Legal Ohms. 

Resistance, Carbon. A resistance, a substitute for a resistance 
coil; it is made of carbon, and is of various construction. In the 
Brush dynamo regulator a set of four vertical piles of plates of 
retort carbon, q. v., is used as a resistance, whose resistance is 
made to vary by changing the pressure. This pressure automatic- 
ally increases as the current strength increases, thus reducing 
the resistance. 



464 STANDARD BIvBCTRICAIy DICTIONARY. 

Resistance Coil, Standard. A standard or resistance issued by 
the Electric Standard Committee of Great Britain. The cut shows 
the standard ohm. It is formed either 
of German silver, or of an alloy of silver, 
66.6 per cent, and platinum, 33.4 per cent. 
The wire is insulated and doubled before 
winding as described before. (See Coil, 
Resistance.) The two ends of the wire are 
soldered, each one to a heavy copper 
wire or rod r. The whole coil is en- 
closed in a brass case, and is enclosed 
with paraffine melted mat A. A place for a 
thermometer is provided at t. By im- 
mersing the lower part of the case B in 
water of different degrees of heat any 
desired temperature can be attained. 

Resistance, Combined. The actual 
resistance of several parallel conductors 
Fig. 292. Standard Ohm Coil, starting from the same point and ending 
at the same point. If the individual resist- 
ance be ad c d and the combined resistance be x then we 

have • 1 

x-=- 




1 1 1 1 

¥ + T + 7~ + ¥ 

Synonym — Joint Resistance. 



Resistance, Critical. In a series wound dynamo the resistance 
of the outer circuit above which the machine will refuse to excite 
itself. 

Resistance, Dielectric. The mechanical resistance of a dielec- 
tric to the tendency to perforation or to the strains due to electri- 
fication. This is a phase of mechanical resistance, and is distinct 
from the electrical or ohmic resistance of the same substance. 

Resistance, Digney Unit of. The resistance of an iron wire, 1 
kilometer long, 4 millimeters diameter, temperature unknown. 
It is equal to 9. 163 legal ohms. 

Resistance, Electrolytic. The resistance of an electrolyte to 
the passage of a current decomposing it. It is almost entirely 
due to electrolysis and is added to by counter-electro-motive force, 
yet it is not treated specifically as such, but as an actual resistance. 
When a current of a circuit of too low voltage to decompose an 
electrolyte is caused by way of immersed terminals to pass through 
an electrolyte the resistance appears very high and sometimes 
almost infinite. If the voltage is increased until the electrolyte is 



STANDARD ELECTRICAL DICTIONARY. 



465 



decomposed the resistance suddenly drops, and what should be 
termed electrolytic resistance, far lower than the true resistance, 
appears. 

Resistance, English Absolute or Foot=Second Unit of. A 



foot 
second 



X io 7 , 



unit based on the foot and second. It is equal to 
being based on these dimensions. 
It is equal to .30140 legal ohm. 

Resistance, Equivalent. A resistance equivalent to other 
resistances, which may include counter-electro-motive force. 

Resistance, Essential. The resistance of the generator in an 
electric circuit ; the same as internal resistance. 

Resistance, External. In an electric circuit the resistance of 
the circuit outside of the generator, or battery. 
Synonym — Non-essential Resistance. 

Resistance Frame. An open frame rilled with resistance coils 
of iron, or German silver wire. It is used as a resistance for 




Fig"- 293. Resistance Frame. 

dynamos and the larger or working class of plant. The coils are 
sometimes connected so that by a switch moving over a row of 



466 



STANDARD ELECTRICAL DICTIONARY. 



studs one or more can be thrown into series according to the stud 
the switch is in contact with. 



Resistance, German Mile Unit of. 

yards of iron wire yb inch in diameter, 
ohms. 



The resistance of 8,238 
It is equal to 56.81 legal 




Fig. 394. 
Hittorf's Resistance. 



Resistance, Hittorf's. A high resistance, often a megohm, com- 
posed of Hittorf's solution, q. v. It is con- 
tained in a vertical glass tube near whose 
upper and lower ends are electrodes of 
metallic cadmium attached to platinum wires. 
The cadmium is melted in glass tubes, the 
platinum wire is inserted into the melted 
metal and the tube is broken after all is solid. 
The resistance should show no polarization 
current. 

Resistance, Inductive. A resistance in 
which self-induction is present ; such as a coil 
of insulated wire wound around an iron core. 

Resistance, Insulation. The resistance of 
the insulation of an insulated conductor. It 
is stated in ohms per mile. It is determined 
by immersing a section of the line in water 
and measuring the resistance between its con- 
ductor and the water. The section must be of known length, and 
its ends must both be above the liquid. 

Resistance, Internal. The resistance of a battery, or generator 
in an electric circuit as distinguished from the resistance of the rest 
of the circuit, or the external resistance. 

Synonym — Essential Resistance. 

Resistance, Jacobi's Unit of. The resistance of a certain cop- 
per wire 25 feet long and weighing 345 grains. 
It is equal to .6296 legal ohm. 

Resistance, Matthiessen's Meter=gram Standard. The resist- 
ance of a pure hard drawn copper wire of such diameter that one 
meter of it weighs one gram. It is equal to .1434 Legal Ohms 
at o°C. (32°F.) 

Resistance, Matthiessen's Unit of. The resistance of a stand- 
ard mile of pure annealed copper wire 1-16 inch diameter, at a 
temperature of 15. 5 C. (6o° F.) 

It is equal to 13.44 legal ohms. 

Resistance, Meter=millimeter Unit of. The resistance of a wire 



STANDARD ELECTRICAL DICTIONARY. 467 

of copper one meter long and one square rnillinieter in section. It 
is equal to .02057 ohms at o° C. (32 F.) The term may also be 
applied to the resistance of similar sized wire of other metals. 

Resistance, Mil=foot Unit of. The resistance of a foot of copper 
wire one-thousandth of an inch in diameter. It is equal to 9.831 
ohms at o° C. (32 F.) The term may also be applied to the resist- 
ance of similar sized wire of other metals. 

Resistance, Nonessential. The resistance of the portion of 
an electric circuit not within the generator ; the same as external 
resistance. 

Synonym — External Resistance. 

Resistance, Non=inductive. A resistance with comparatively 
little. or negligible self-induction. 

Resistance of Human Body. The resistance of the human 
body is largely a matter of perfection of the contacts between its 
surface and the electrodes. It has been asserted that it is affected 
by disease. From 350 to 8,000 ohms have been determined as 
resistances, but so much depends on the contacts that little value 
attaches to the results. 

Resistance, Ohmic. True resistance measured in ohms as 
distinguished from counter-electro-motive force, q. v. The latter 
is called often spurious resistance. 

Synonym — True Resistance. 

Resistance, Reduced. The resistance of a conductor reduced 
to ohms, or to equivalent lengths of a column of mercury, 1 square 
millimeter in cross area. 

Resistance, Siemen's Unit of. The resistance of a column of 
mercury 1 meter long and 1 square millimeter cross-sectional area 
ato°C. (32 F.) 

It is equal to .9431 legal ohm. 

Resistance, Specific. The relative resistance of a substance. 
It is expressed as the actual resistance of a cube of the substance 
which is one centimeter on each edge. For metals it is usually 
expressed in microhms, for liquids in ohms. 

The resistances of a specified length of wire of specified diameter 
of different substances is often given, and is really a particular way 
of stating specific resistances. 

Synonym — Specific Conduction Resistance. 

Resistance, Spurious. The counter-electro-motive force, q. v., 
operating to prevent a current being produced of what should be its 
full strength were the true resistance and actuating electro-motive 



468 STANDARD ELECTRICAL DICTIONARY. 

force only concerned. Such counter-electro-motive force may be 
treated as a spurious resistance and such a value in ohms assigned 
to it as would correspond to its proper effect. 

In its effect on opposing a current and in resisting its formation 
it differs from true resistance. The latter in diminishing current 
strength absorbs energy and develops heat ; spurious resistance 
opposes and diminishes a current without absorption of energy or 
production of heat. 

Resistance, Steadying. When arc lamps are connected in 
parallel or multiple arc a small resistance coil is sometimes placed 
in series with each lamp for steadying purposes. It reduces the 
percentage of variation of resistance in each lamp, which may be 
caused by a change in the position of the carbons. 

Resistance, Swiss Unit of. A unit constructed by the "Ad- 
ministration Suisse " based on the same data as the Breguet and 
the Digney Units. (See Resistance y Digney Unit of.) 

It is equal to 10.30 legal ohms. 

Resistance, Thomson's Unit of. A unit of resistance based on 
the foot and second. 

It is equal to .3166 legal ohm. 

Resistance, Unit. Unit resistance is that of a conductor in 
which unit current is produced by unit electro-motive force. 

Resistance, Varley's Unit of. The resistance of a standard 
mile of a special copper wire T ^ inch diameter. 
It is equal to 25.33 ohms. 

Resistance, Weber's Absolute Unit. A metric system unit ; 
meter 
second 

It is equal to .9089 legal ohm. 

Resonance, Electric. A set of phenomena known as the Hertz 
experiments are grouped under this title, which phenomena are 
incidents of and depend on the propagation of electric waves 
through wires or current conductors, as well as through the ether. 
Ordinarily a wire is only a seat of current, and is in its nature in- 
consistent with wave propagation through its mass. Such waves 
are virtually confined to the exterior of the wire. The point is 
that the current-producing force is supposed to enter the wire at 
all points from without, the current not being produced by an end- 
push. Hence in rapidly recurring waves which are produced by a 
rapidly pulsatory or alternating current, no time is afforded for the 
current-producing force, in this case the wave-producing force, to 
penetrate into the substance of the wire. In one of his experi- 



STANDARD ELECTRICAL DICTIONARY. 



469 



ments Dr. Hertz surrounded a wire by a glass tube chemically 
silvered. The coating was so thin as to be translucent. Through 
this metallic layer a current could be induced in the wire in its 
interior. Any mechanical layer of metal took up the induction 
itself, and protected the central wire. This gave a clue to the 
thickness of metal penetrated by the rapid induced waves used by 
Dr. Hertz. 

The method used for the production of rapid oscillations is the 
following. To the terminals of an induction coil two metal spheres 
A A 1 are connected as shown. This apparatus is termed the exciter ; 




Electrical Resonanxe Exciter. 



in its discharge a series of isochronous discharges takes place, alter- 
nating in direction. The period of duration T of a single one is 
given by the formula T= 2 it y LC, in which C is the capacity 
and L is the self-induction. The spheres may be 30 centimeters 
(11. 8 inches) in diameter, connected each to" conductors .5 centi- 
meter (.2 inch) in diameter and 40 centimeters (15.7 inches) long 
each. For the length of an undulation the formula gives for this 
apparatus 4.8 meters (15.75 feet) as the length of a wave, assuming 
for them the velocity of propagation equal to that of light. The 
exciter may have 10,000 times the rate of oscillation possessed by 
the plain induction coil. 

When this apparatus is worked it produces induced waves in 
every neighboring conductor. The resonance effects appear in the 
size of the spark induced. Thus a wire bent into a circle with its 
ends nearly touching will give a spark, but if made of proper elec- 
trostatic capacity, corresponding with the particular waves em- 
ployed, the spark will be very much larger. The ring, with its 
spark gap is termed a resonator. It is used as an explorer to trace 
the waves. 

Waves thus produced are transmitted by stone walls and non- 
conductors in general. A plate of zinc reflects part and transmits 
part. The reflected waves can be traced by the resonator, their 



47Q 



STANDARD ELECTRICAL DICTIONARY. 



angle of reflection being equal to their angle of incidence. They 
can be received by one parabolic reflector, reflected to another and 
brought to a focus. They can be reflected so as to produce inter- 
ference or loops and nodes, and the loops and nodes can be traced 
by the resonator. By a prism of asphalt they are refracted exactly 
like light. 

From all this it is concluded that an additional proof is furnished 
of the identity of light and electro-magnetic waves, and a very 
strong experimental proof of Maxwell's theory of light is furnished. 

Synonym — Hertz's Experiments. 

Resonator, Electric. A small open electric circuit, with ends 
nearly touching. When exposed to electric resonance, or to a sym- 
pathetic electric oscillatory discharge, a spark passes from across 
the gap. The production of this spark is altogether a matter of the 
inductance of the resonator. The simplest form is a circle of cop- 
per wire with its ends nearly touching. The length of the gap is 




Fig. 296. Electrical Resonator. 

adjustable by bending. A screw adjustment may also be provided. 
Another form is shown in the cut, Fig. 296. Here sheets of tin- 
foil are used to regulate the electrostatic capacity, while at m is 
shown the finger piece for regulating the size of the spark gap a. 
Synonym — Spark Micrometer. 

Resultant. The line indicating the result of the application of 
two or more forces to a point. Its direction and length give the 
elements of direction and intensity. (See Forces, Resolution of— 
Forces, Composition of ^Components.) 

Resultant Polarity. The magnetic polarity imparted to a mass 
of iron acted on by two or more separate inducing forces or cur- 
rents. It appears in dynamos and motors. The final polarity is 
the resultant of the inducing effect of the field magnet poles and of 
the windings. 

Retardation. In telegraphy a retardation of the rate of trans- 
mission of signals. It is due to several causes. 

(a) The self-induction of the circuit, especially if it includes 



STANDARD ELECTRICAL DICTIONARY. 471 

many electro-magnets, produces extra currents (see Currents, 
Extra.) These are opposed to the main current on closing it and 
hence retard the action. They are in the same direction on open- 
ing it and hence again retard the action. 

(b) Every line has a certain static capacity. This is affected by 
the proximity of the lines to the earth. For each signal electricity 
has to be charged upon the line until the line is charged to its end 
with a certain proportion of the initial density. This charging 
takes time and hence introduces retardation. 

(c) The cores of the electro-magnets of the relays or sounders 
are not instantly magnetized and demagnetized. This magnetic 
lag, q.- v., introduces retardation. 

Retardation of Phase. The fractional lagging behind of waves 
or alternating currents ; by lagging behind a portion of a wave 
length the corresponding phases, as of full amplitude, are kept back 
or retarded. The phase of current intensity may be retarded with 
reference to the electro-motive force by the introduction of trans- 
formers of high capacity with high resistance on open secondary 
circuits. 

Retentivity. Coercitive or coercive force ; by virtue of which 
steel retains its magnetism. It is the more modern name, " coer- 
cive force " as a term being rejected by many. 

Synonyms — Coercive Force — Coercitive Force. 

Retort Carbon. Carbon deposited in coal gas retorts from 
decomposition of the hydrocarbons. It is a very hard, pure form, 
and is of graphitic modification. Owing to its great hardness it is 
little used for electrical purposes, the molded carbons being easier 
to make. The deposition occurs in the regular ^ gas-making 
process, and is a disadvantage to the working. 

Return. A line or conductor which is supposed to carry cur- 
rent back to its starting point, after it has traversed a line, it may 
be a wire or the grounding of the ends of a line may make the 
earth act as a return, termed ground- or earth-return. The best 
distinction of a return is to so term the portion of a circuit on 
which no apparatus is placed. 

Reversibility. The principal in virtue of which a device for pro- 
ducing a given form of energy can absorb the same and do work. 
The reversibility of the dynamo is its quality in virtue of which it 
can act as a current generator, thereby converting mechanical 
energy into electric energy, or if a current is passed through it, it 
rotates, doing work, and thereby converting electric energy into 
mechanical energy. The knowledge of this principle can be 
traced back to Jacobi in 1850. 



472 STANDARD ELECTRICAL DICTIONARY. 

Reversible Bridge. A form of Wheatstone's Bridge adapted for 
reversal of the positions or interchange of the proportionate arms, 
q. v. , so that the accuracy of the coils can be tested. 

RheochorcL An apparatus by means of which variable quanti- 
ties of wire are thro wn into the circuit ; a rheostat using wire. (See 
Rheostat, Wheatstone's.) 

Rheometer. A galvanometer. {Obsolete.) 

Rheomotor. A source of current ; a current generator ; a 
producer of potential difference. {Obsolete.) 

Rheophore. The portion of an active circuit capable of deflect- 
ing a magnetic needle. This properly includes all of the metallic 
conductor of a circuit. ( Obsolete. ) 

Rheoscope. A galvanoscope ; an instrument for qualitatively 
detecting potential difference, fall or rise. (See Galvanoscope.) 

Rheostat. An adjustable resistance ; an apparatus for changing 
the resistance without opening the circuit. Its action may 
depend on the introduction of variable lengths of mercury column, 
of some other liquid, or of wire into a circuit. (See Rheostat, 
Wheatstone's.) 

Rheostat Arm. The third arm of known resistance in a Wheat- 
stone bridge. (See Proportionate Arms.) 

Rheostatic Machine. An apparatus for increasing potential 
difference. It consists of a number of static condensers. They are 
charged in multiple arc or in parallel, and are discharged in series. 
Secondary batteries may be used for the charging ; thus a static 
effect is produced from a galvanic battery. 

Rheostat, Wheatstone's. This apparatus consists of two cylin- 
ders, one, A, made of brass, the other, B, of wood, with a spiral 
groove. At its end is a copper ring a. A fine brass wire has one 
end attached to this ring. Its other end is fastened at e, and it is 
wound as shown ; n and o are binding screws connected, one with 
the cylinder-ring a, the other with the brass cylinder, A. The cur- 
rent entering at o> traverses the wire on B, as there the windings 
are insulated by the grooves, thence it passes to m and by A y 
whose metal short circuits all the wire on it, to the binding-post 
n. The handle, d } is turned one way or the other to regulate 
the length of the wire through which the current must pass. On 
each cylinder there is a square head, one of which is shown at c> so 
that the handle can be shifted from one to the other as required ; 
to A if the wire is to be wound on that cylinder, to B if the reverse 
is desired. 



STANDARD ELECTRICAL DICTIONARY. 473 

Rheotome. An automatic circuit breaker, one which rapidly 
opens and closes a circuit, as in the case of the primary of an induc- 
tion coil an interrupter. {Obsolete.) 




Fig. 297. Wheatstone's Rheostat. 

Rheotrope. A pole changer, current reverser, or commutator, 
e. g., such as the commutator of an induction coil. {Obsolete.) 

Rhigolene. A petroleum product ; a hydrocarbon of low boil- 
ing point. Its vapor is used in flashing (q. v.) carbon filaments 
for incandescent lamps. 

Rhumbs. In a mariners' compass, the thirty-two points, desig- 
nated, north, north by east, north north east, etc. (See Compass 
Mariners — Compass, Points of the. ) 

Rhumkorff Coil. The induction coil, q. v. 

Rigidity, Molecular. The tendency of molecules to resist 
rotation or change of position ; the assumed cause of magnetic 
coercive force, or retentivity. 

Ring Contact. A contact formed by a terminal clip in the 
shape of a ring, split or cut at one point so that its ends tend to 
spring together. The other terminal is a bar which passes into the 
cut and is tightly pressed by the elastic ring. 

Ring, Faraday. A closed ring of iron used as the core of a 
transformer or induction coil. The term is derived from Faraday's 



474 STANDARD ELECTRICAL DICTIONARY. 

classic experiment with such an apparatus when he produced a 
spark by induction in a secondary circuit. 



Fig". 298. Switch with Ring Contacts. 

Roaring. A term applied to the noise sometimes produced in a 
voltaic arc, when the electrodes are close together and a heavy 
current is passing. 

Rocker. In a dynamo the movable piece, mounted concentric- 
ally with the commutator, and carrying the rocker-arms and brush- 
holders. By moving it the brushes are adjusted for proper lead. 

Rocker Arms. The arms projecting from a rocker and each 
carrying one of the brush-holders. 

Roget's Spiral. An experimental apparatus for illustrating the 
mutual attraction of currents going in like direction. A cylindri- 
cal helix or spiral of wire is suspended by one end. Its lower end 
just dips into a mercury cup. An active circuit is connected, one 
terminal to the upper end, the other terminal to the mercury cup, 
bringing the apparatus in series into the circuit. The current as 
it passes causes the coil to shorten, each spiral attracting its neigh- 
bors. This breaks the circuit by drawing the lower end out of the 
mercury cup. The current being cut off the coils cease to attract 
each other, and the end dips into the mercury cup again. This 
closes the circuit, the coils again attract each other and the same 
sequence follows and is repeated over and over again. A bright 
spark is produced at each break of the mercury contact. 

Rotation of Liquids, Electro=dynamic. By passing a current 
through a liquid, such as dilute sulphuric acid, it rotates if exposed 
to the induction of a current flowing at right angles to it. The 
condition resolves itself into a liquid traversed by horizontal cur- 



STANDARD ELECTRICAL DICTIONARY. 475 

rents from centre to circumference or vice versa, rotated by a current 
passing through a circular conductor below it. 

Rotation of Liquids, Electro=magnetic. The rotation produced 
in a liquid carrying centripetal or centrifugal currents by an electro- 
magnet. It is practically an intensification of electro-dynamic 
rotation. (See Rotation of Liquids, Electro-dynamic) 

Rubber. In a frictional electric machine the cushion of leather 
which is pressed against the plate as it rotates. 

S. (a) Symbol for second. 

(5) Symbol for space, or length ; L, is preferable. 
(c) Symbol for south-seeking pole of a magnet. 

Saddle Bracket. A bracket carried on the top of telegraph poles, 
carrying an insulator for the upper wire. 

Safety Device, (a) A device to prevent overheating of any 
portion of a circuit by excess of current. It generally consists of a 
slip of fusible metal which if the current attains too much strength 
melts and opens the circuit. To ensure its breaking a weight is 
sometimes suspended from the strip. In one form an insulated Ger- 
man silver wire is wrapped around the end of the fusible strip a num- 
ber of times and its end is connected to it. The other end of the 
German silver wire connects with the main lead, so that all the cur- 
rent goes through both in series. If the German silver wire 
becomes heated from excess of current the coil wrapped tightly 
around the end of the fusible strip melts it and opens the circuit. 

(6) Lightning arresters, q. v., may be cited under this heading. 
Synonyms — Automatic Cut Out — Safety Fuse, Plug, or Strip. 

Safety Fuse. A strip of metal inserted so as to form part of a 
circuit and of such size that a smaller 
current would heat the regular wire 
of the circuit dangerously, so as to 
cause a conflagration for instance, 
would melt the fuse and open the 
circuit. As it sometimes happens that 
a safety fuse melts without parting 
a weight is sometimes hung upon 

it, so as to break it as it softens. „ _ 

Fig - . 299. Cockburn Safety Fuse. 
Salt. A salt is a chemical com- 
pound containing two atoms or two radicals, which saturate each 
other. One atom or radical is electro-positive referred to the 
other, which is electro-negative. By electrolysis salts are decom- 
posed, the atoms or radicals separating and uniting to form new 
molecules. 




476 



STANDARD ELECTRICAL DICTIONARY. 



Saturated, adj. A liquid is saturated with a substance when 
it has dissolved all that it can, while an excess is present in 
the liquid. It is possible, by dissolving some salts in hot water 
and allowing the solution to cool without access of air, to obtain a 
supersaturated solution. On introduction of a crystal of the salt, 
or often on mere access of air, the solution forms crystals and the 
liquid left is saturated. 

Saw, Electric. A platinum coated steel wire mounted and con- 
nected to be raised to incandescence for cutting purposes. 

Schweigger's Multiplier. An old term for the galvanometer 
as invented by Schweigger soon after Oerstedt's discovery. 

Scratch Brushes. Brushes for cleaning the surface of articles 
to be electroplated to give a good metallic surface suitable for 
deposition. They have often wire instead of bristles. 

Screen, Electric. A large plate or a hollow case or cage of 




Fig. 300. Wire Gauze Electric Screen. 
conducting material connected with the earth, and used to protect 
any body placed within it from electrostatic influences. 



STANDARD ELECTRICAL DICTIONARY. 477 

If within a hollow conducting sphere an electrified body is 
placed, the inner surface of the sphere will be charged with elec- 
tricity of opposite kind to that of the sphere, and the outer surface 
with "the same kind as that of the sphere. Thus the sum of the 
electricities called into action by induction is zero. The two inner 
charges are bound to each other. The induced charge on the outer 
surface of the sphere is all that has any effect on objects in the 
outer air. 

If the outer surface is connected to the earth it becomes dis- 
charged, and however highly electrified the body introduced into 
the sphere and the inner surface of such sphere may be, they pro- 
duce no external effects, as they are bound one to the other. • 

If the sphere is connected to the earth and an unelectrified object 
is placed within it, such object will be perfectly shielded from the 
effects of an outer electrostatic field. Perforated tinfoil or wire 
gauze has just as good a result. A large plate of metal connected 
to the earth has the same effect. The screen whether plane or 
hollow simply retains a bound charge due to the field of force, 
thereby neutralizing it, and the electricity of the opposite sign 
escapes to the earth. Thus a true shielding or screening effect is 
produced. 

In the cut an experiment is shown in which an electric screen is 
carried by a Leyden jar. Pith balls are suspended outside and 
inside of it. By the approach of an electrified body the outer pith 
balls will diverge, while no effect is produced upon the inner ones. 

Secondary Actions. In electrolysis the direct products of the 
electrical decomposition are not always obtained at the electrodes, 
but products due to their reaction on the water and other chemicals 
may appear. These constitute secondary actions. Thus if a solu- 
tion of copper sulphate is electrolyzed with platinum electrodes, 
metallic copper appears at one pole and sulphuric acid and oxygen 
gas at the other. But the products of electrolysis by the current 
are copper (Cu) and sulphion (SO J. The latter reacting on water 
sets free oxygen gas and forms sulphuric acid. The latter is a 
secondary action. 

Secondary Generator, [a) An alternating current converter 
generating a so-called secondary current. 

(b) A secondary battery, q. v., may be thus termed. 

Secondary, Movable. The term movable secondaries has been 
applied to rings, spheres and discs of conducting material, such as 
copper, whose behavior when near the pole of an electro-magnet 
traversed by an alternating current, have been studied by Elihu 
Thomson. Such masses are subjected to very peculiar movements 



478 STANDARD ELECTRICAL DICTIONARY. 

and mutual reactions. As the phenomena are due to induced cur- 
rents the above term has been applied to the masses in which the 
currents are induced. 

Secondary Plates, Colors of. In a secondary battery of the 
lead plate type, the color of the plates is a good indication of the 
condition of the battery. The negative plate should be brown or 
deep-reddish, the other should be slate-colored. 

Secondary Poles. Poles sometimes found in magnets existing 
in positions intermediate between the end or true poles. 
Synonym — Consequent Poles. 

Seebeck Effect. The production of a current by heating the 
junction of two different metals forming part of a circuit, or the 
thermo-electric production of current, is stated as the Seebeck 
effect, having been discovered by that investigator. 

Selenium. A non-metallic element. It is interesting electric- 
ally on account of the changes its electric resistance undergoes 
when it is subjected to light. 

In one set of experiments it was found that diffused light caused 
the resistance to fall in the ratio of n to 9. Full sunlight reduced 
it to one-half. Of the spectrum colors red was most powerful and 
the ultra red region still more strongly affected its resistance. 

The effect produced by exposure to light is instantaneous, but 
on removal to the dark only slowly disappears. 

A vessel of hot water was found to have no effect, showing that 
short ether waves are essential to the effect. 

Selenium Cell. A selenium resistance box. Vitreous selenium 
is made by keeping ordinary selenium for some hours at a temper- 
ature of about 220 C. (428 F.) after fusing. It is placed in an 
electric circuit as part of the conductor. 

Its resistance can then be determined. It decreases in sunlight 
to about one-half its resistance in the dark. 

The selenium cell is used in the Photophone, q. v. Otherwise 
it is little more than a subject of experiment. 

Selenium Eye. A model eye in which selenium in circuit with 
a battery and galvanometer takes the place of the retina of the 
human eye. 

Self =repulsion. When a body is electrified each molecule repels 
its neighbor and the condition in question is thus designated. An 
electrified soap-bubble expands in virtue of self-repulsion. 

Semiconductors. Substances which conduct static electricity 
poorly, but quite appreciably and beyond the extent of leakage. 



STANDARD ELECTRICAL DICTIONARY. 479 

The following are examples : Alcohol and ether, powdered glass, 
flowers of sulphur, dry wood, paper, ice at o° C. (32 F.) 

Sensibility. The measure of the effect of a current upon a 
galvanometer, or any similar case. 

Sensitiveness, Angle of Maximum. Every galvanometer has 
its angle of maximum sensitiveness, which is the angle of deflec- 
tion at which a small increment of current will produce the greatest 
deflection. For every tangent galvanometer 45 ° is the angle in 
question. In using a galvanometer for direct reading methods it 
is an object to have it work at its angle of maximum sensitiveness. 

Separately Excited Dynamo. A dynamo-electric machine 
whose field magnet is excited from an outside source, which may 
be another dynamo or a battery. Alternating current dynamos are 
often of this description. 

Separate Touch. In magnetism a method of inducing magnet- 
ism in a steel bar. The opposite poles of two magnets are applied 
at the center of the bar to be magnetized, but without touching 
each other, and are drawn apart to its ends. They are returned 
through the air and the process is repeated a number of times and 
on both sides of the bar if necessary. 

Separation of Electricities. Under the double fluid theory of 
electricity the action of electrification in accumulating positive 
electricity in one conductor and negative on the other of the 
excited surfaces of tw T o conductors. 

Separator. India rubber bands or other forms used in batteries 
to keep the plates from touching in the cell ; especially applied to 
secondary batteries, where the plates are so near together as to 
require separators to prevent short circuiting. 

Series, (a) Arranged in succession as opposed to parallel. Thus 
if a set of battery jars are arranged with the zinc of one connected 
to the carbon of tie next one for the entire number, it is said to be 



Fig". 301. Series Connection. 

arranged in series. When incandescent lamps are arranged in 
succession so that the current goes through one after the other they 
are arranged in series. 

The opposite of parallel, q. v., or multiple arc,q.v.; it may 
be used as a noun or as an adjective. 

(6) See Electro-Chemical Series ; (c) Thermo- Electric Series 
id) Electrostatic Series ; (e) Electro-motive Series. 

Synonym — Cascade Connection (but little used.) 



480 STANDARD ELECTRICAL DICTIONARY. 

Series=multiple. Arrangement of electric apparatus, in which 
the parts are grouped in sets in parallel and these sets are con- 
nected in series. It is used as a noun, as ' ' arranged in series-multi- 
ple," or as an adjective, as " a series-multiple circuit or system." 



Fig. 302. Series-multiple Connection. 

Service Conductors. In electric distribution the equivalents of 
service pipes in the distribution of gas ; wires leading from the 
street mains to the houses, where current is to be supplied. 

Serving. The wrapping or winding of a cable composed of 
small size wire, laid closely and smoothly with a tool called a 
serving mallet, or serving block, or by machinery. It serves to 
protect the cable from wear. 

Shackle. In telegraph lines a swinging insulator bracket for use 
where wires make an angle with the pole. A journal box is 
attached to the pole, like half of a gate hinge. To this a short iron 
arm is pivoted so as to be free to swing through a considerable 
angle. At its end an insulator is carried to which the wire is 
attached. The shackle swings into line with the wire, or takes a 
position for two wires corresponding to the resultant of their direc- 
tions of pull. 




Fig- 303- Double Shackle. 

Shadow, Electric. A term applied to a phenomenon of high 
vacua. If an electric discharge is maintained in a Crookes' tube 
the glass opposite the negative electrode tends to phosphoresce. A 
plate of aluminum, used also as the positive electrode, protects the 
glass directly behind it so as to produce the effect of a shadow. 

Synonym — Molecular Shadow. 



STANDARD ELECTRICAL DICTIONARY. 481 

Sheath for Magnet Coils. In 1867 C. E. Varley proposed the 
use of a copper sheath surrounding a magnet core to diminish self- 
induction. It has since been used by Brush and others. Some- 
times metallic foil is laid between the successive coils of wire. 

Synonym — Mutual Induction Protector. 

Sheath for Transformers. A protective sheath of copper, 
interposed between the primary and secondary circuits of an alter- 
nating current transformer. It is connected to the earth. If the 
primary coil loses its insulation before it can leak to the secondary 
it is grounded. This protects the secondary circuit from the high 
electro- motive force of the prirnary circuit. 

Shellac. A resin ; produced as an exudation upon the branches 
of certain Asiatic trees, such as the banyan {Ficus religiosa). It 
is due to punctures in the bark of the trees in question, which 
punctures are made by the female of the insect coccus ficus or c. 
lacca. 

Commercial shellac contains about 90 per cent, of resinous 
material, the rest is made up of wax, gluten, coloring matter and 
other substances. 

Shellac is soluble in alcohol, and in aqueous solutions of 
ammonium chloride, of borax and in strong ammonia solution. 
Long standing is required in the case of the last named solvent. 
Dilute hydrochloric and acetic acids dissolve it readily ; nitric acid 
slowly ; strong sulphuric acid is without action on it. Alkalies 
dissolve it. 

In electric work it is used as an insulator and dielectric. Its 
alcoholic solution is used to varnish glass plates of influence 
machines, for the coils of induction coils and similar purposes. 

Resistance in ohms per centimeter cube at 28 C. (82.4 F.) 
(Ayrton), 9000 X io 12 

Specific Inductive Capacity (Wiillner), 2.95 to 3.73 

The same substance in less pure forms occurs in commerce, as 
stick lac, lump lac, seed lac, button lac. 

Shellac Varnish. Solution of shellac in alcohol ; methylic 
alcohol (wood alcohol or wood naphtha) is often used as solvent. 

Dr. Muirhead recommends button lac, dissolved in absolute 
alcohol, and the top layers decanted. For highest insulation he 
dissolves the lac in ordinary alcohol, precipitates by dropping 
into water, collects the precipitate, dries and dissolves in absolute 
alcohol. 

Shielded, adj. An electric measuring instrument of the 
galvanometer type is shielded when it is so constructed that its 
indications are not seriously affected by the presence of neigh- 



482 STANDARD ELECTRICAL DICTIONARY. 

boring magnets or by fields of force. Shielding can be effected by 
using a very strong permanent magnet to produce a field within 
which the magnetic needle moves and which reacts upon it, or by 
enclosing the instrument in a thick iron box. 

S. H. M. Symbol or abbreviation for "simple harmonic 
motion." 

Shock, Break. A term in electro-therapeutics ; the shock 
received when an electric circuit, including the patient in series, is 
broken or opened. 

Synonym — Opening Shock. 

Shock, Electric. The effect upon the animal system of the 
discharge through it of electricity with high potential difference. 
Pain, nervous shock, violent muscular contortions accompany it. 
Of currents, an alternating current is reputed worse than a direct 
current ; intermediate is the pulsatory current. 

The voltage is the main element of shock, amperage has also 
some direct influence. 

Shock, Static. A term in electro-therapeutics. The application 
of static discharges from small condensers or Ley den jars to a 
patient who is insulated from the ground with one electrode 
applied to the conducting surface on which he rests, while the 
other, a spherical electrode, is brought near the body so as to pro- 
duce a disruptive or spark discharge. 

Short Circuit. A connection between two parts of a circuit, 
which connection is of low resistance compared to the intercepted 
portion. The term is used also as a verb, as "to short circuit a 
lamp." 

Short Circuit Working. A method of working intermittently 
an electro-magnet so as to avoid sparking. It consists in providing a 
short circuit in parallel with the magnetic coils. This short circuit 

Fig. 304. Diagram Illustrating Short Circuit Working. 

is of very low resistance. To throw the magnet into action the 
short circuit is opened ; to throw it out of action the short circuit 
is closed. The shunt or short circuit must be of negligibly small 
resistance and inductance. 



STANDARD ELECTRICAL DICTIONARY. 483 

Shovel Electrodes. Large plate electrodes used in a medical 
bipolar bath. (See Bath, Bipolar.) 

Shunt. In a current circuit a connection in parallel with a 
portion of the circuit. Thus in a dynamo a special winding for 
the field may have its ends connected to the bushes, from which 
the regular external circuit also starts. The field is then wound in 
shunt with the armature. In the case of a galvanometer a resist- 
ance coil may be put in parallel with it to prevent too much current 
going through the galvanometer ; this connection is a shunt. 

The word is used as a noun, as "a shunt," or " a connection or 
apparatus in shunt with another," and as an adjective, as " a shunt 
connection," or as a verb, as "to shunt a battery." 

Shunt Box. A resistance box designed for use as a galvanom- 
eter shunt. (See Shunt, Galvanometer.) The box contains a 
series of resistance coils which can be plugged in or out as required. 

Shunt, Electro=magnetic. In telegraphy a shunt for the re- 
ceiving relay consisting of the coils of an electro-magnet. It is 
placed in parallel with the relay. Its poles are permanentlv con- 
nected by an armature. Thus it has high self-induction. 

On opening and closing the circuit by the sending key, extra 
currents are produced in the shunt. The connections' are so 
arranged that on making the circuit the extra current goes through 
the relay in the same direction as the principal current, while on 
breaking the circuit the induced current goes in the opposite 
direction. 

Thus the extra currents accelerate the production and also the 
cessation of signalling currents, tending to facilitate the operations 
of sending despatches. 

Shunt, Galvanometer. A resistance placed in parallel with a 
galvanometer, so as to short circuit its coils and prevent enough 
current passing through it to injure it. By knowing the resistance 
of the shunt and of the galvanometer coils, the proportion of cur- 
rent affecting the galvanometer is known. This gives the requisite 
factor for calculation. (See Multiplying Power of Shunt.) 

Shunt Ratio. The coefficient expressing the ratio existing 
between the current in a shunt and in the apparatus or conductor 
in parallel with it. (See Multiplying Power of Shunt.) 

Shunt Winding. A dynamo or motor is shunt- wound when the 
field magnet winding is in shunt or in parallel with the winding of 
the armature. 

Shuttle Current. A current alternating in direction ; an alter- 
nating current. 



484 STANDARD ELECTRICAL DICTIONARY. 

Side=Flash. A bright flashing lateral discharge from a con- 
ductor conveying a current due to a static discharge. 

Sighted Position. In an absolute electrometer (see Electrom- 
eter, Absolute) the position of the balanced arm carrying the 
movable disc or plate, when the disc and guard plate are in one 
plane. The cross-hair on the lever-end is then seen midway between 
two stops, or some other equivalent position is reached which is 
discerned by sighting through a magnifying glass or telescope. 

Silver. A metal ; one of the elements ; symbol Ag. ; atomic 
weight, 108 ; valency, i ; equivalent, 108 ; specific gravity, 10.5. It 
is a conductor of electricity. 

Relative resistance , an nealed , 1 . o 

Specific Resistance, annealed, at o° C. (32 F.) 1.504 microhms. 

Resistance of a wire at o° C. (32 F.), 

Annealed. Hard Drawn. 

(a) 1 foot long, weighing 1 grain, .2190 ohms. .2389 ohms. 

(6) 1 foot long, T jfcj; inch thick, 9.048 " 9.826 " 

(c) 1 meter long, weighing 1 gram, .1527 " .1662 " 

(d) 1 meter long, 1 millimeter thick, .01916 " .02080 " 
Resistance annealed of a i-inch cube, ato° C. (32°F.) .5921 microhms. 

Percentage increase in resistance per degree C. 

(1.8 F.) at about 20 C. (68° F.), annealed, 0.377 per cent. 
Electro-chemical equivalent, (Hydrogen = .0105) 1,134 mgs. 

Silver Bath. A solution of a salt of silver for deposition in 
the electroplating process. The following is a typical formula : 
Water, 10. o parts by weight. 

Potassium Cyanide, 5 " " 

Metallic Silver, 1%, " " 

The silver is first dissolved as nitrate and converted into cyanide 
and added in that form, or for 1% parts metallic silver we may 
read : 

Silver cyanide, 3 parts by weight. 

While many other formulas have been published the above is 
representative of the majority. Other solvents for the silver than 
potassium cyanide have been suggested, such as sodium hyposul- 
phite, but the cyanide solution remains the standard. 

Silver Stripping Bath. Various baths are used to remove 
silver from old electroplated articles. Their composition depends 
upon the base on which the metal is deposited. Silvered iron 
articles are placed as anodes in a solution of 1 part potassium cyan- 
ide in 20 parts of water. As kathode a silver anode or a copper one 
. lightly oiled may be used. From the latter the silver easily rubs 
offo For copper articles a mixture of fuming sulphuric acid and 



STANDARD ELECTRICAL DICTIONARY. 485 

nitric acid (40 Beaum£) may be used. The presence of any water 
in this mixture will bring about the solution of the copper. Or 
fuming sulphuric acid may be heated to between 300 and 400 F., 
some pinches of dry pulverized potassium nitrate may be thrown 
in and the articles at once dipped. These methods effect the solu- 
tion of the silver, leaving the copper unattacked. 

Simple Substitution. A method of obtaining a resistance equal 
to that of a standard. The standard is put in circuit with a galva- 
nometer and the deflection is noted. For the standard another 
wire is substituted and its length altered until the same deflection 
is produced. The two resistances are then evidently identical. 
The standard can be again substituted to confirm the result. 

Sine Curve. If we imagine a point moved back and forth 
synchronously with a pendulum, and if such point made a mark 
upon paper, it would trace the same line over and over again. 
If now the paper were drawn steadily along at right angles 
to the line of motion of the point, then the point would trace 
upon it a line like the profile of a wave. Such line is a sine 
curve. It derives its name from the following construction. Let 
a straight line be drawn, and laid off in fractions, such as degrees, 
of the perimeter of a circle of given diameter. Then on each 
division of the line let a perpendicular be erected equal in height 
to the sine of the angle of the circle corresponding to that division; 
then if the extremities of such lines be united by a curve such 
curve will be a sine curve. 

In such a curve the abscissas are proportional to the times, 
while the ordinates are proportional to the sines of angles, which 
angles are themselves proportional to the times. The ordinates 
pass through positive and negative values alternately, while the 
abscissas are always positive. 

Any number of sine curves can be constructed by varying the 
diameter of the original circle, or by giving to the abscissas a 
value which is a multiple of the true length of the divisions of 
circle. If the pendulum method of construction were used this 
would be attained by giving a greater or less velocity to the paper 
as drawn under the pendulum. 

A species of equation for the curve is given as follows : y = sin x. 
In this x really indicates the arc whose length is x, and reference 
should be made to the value of the radius of the circle from which 
the curve is described. It will also be noticed that the equation 
only covers the case in which the true divisions of the circle are 
laid off on the line. If a multiple of such divisions are used, say n 
times, or i-n times, then the equation should read y = n sin x or 
y = sin x 
n 

Synonyms — Curve of Sines — Sinusoidal Curve — Harmonic Curve. 



486 STANDARD ELECTRICAL DICTIONARY. 

Sine Law. The force acting on a body is directly proportional 
to the sine of the angle of deflection when — 

I. The controlling force is constant in magnitude and direction ; 
and 

II. Xhe deflecting force, although variable in its direction in 
space, is fixed in direction relatively to the deflecting body. 

Single Fluid Theory. A theory of electricity. Electricity, as 
has been said, being conveniently treated as a fluid or fluids, the 
single fluid theory attributes electrical phenomena to tfce presence 
or absence of a single fluid. The fluid repels itself but attracts 
matter; an excess creates positive, a deficiency, negative electri- 
fication ; friction, contact action or other generating cause altering 
the distribution creates potential difference or electrification. The 
assumed direction (see Direction) of the current and of lines of 
force are based on the single fluid theory. Like the double fluid 
theory, q. v., it is merely a convenience and not the expression of 
a truth. (See Fluid, Electric, and Double Fluid Theory,) 

Synonym — Franklin's Theory. 

Single Fluid Voltaic Cell. A galvanic couple using only a 
single fluid, such as the Smee or Volta cell. 

Simple Harmonic Motion. Motion of a point or body back 
and forth along a line ; the motion of a pendulum, as regards its 
successive swings back and forth, is an example of harmonic 
motion. 

Sinistrotorsal. adj. The reverse of dextrotorsal,(\. v. A helix 
with left-handed winding, the reverse of an ordinary screw, such 
as a wood-screw or corkscrew. 

Skin Effect. A current of very brief duration does not pene- 
trate the mass of a conductor. Alternating currents for this 
reason are mainly conducted by the outer layers of a conductor. 
The above is sometimes called the skin effect. 

Sled. A contact for electric cars of the conduit system. It is 
identical with the plow, q. v. , but is drawn after the cars instead of 
being pushed along with them. 

Slide Meter Bridge. A name for a Slide Bridge one meter 
long. There are also slide half meter and slide quarter meter 
bridges and others. (See Meter Bridge. ) 

S. N. Code. Abbreviation for single needle code, the telegraphic 
alphabet used with the single needle system. 

Soaking=in=and=out. A term for the phenomena of the residual 
electrostatic charge ; the gradual acquirement or loss by a con- 
denser of a portion of its electrostatic charge. 



STANDARD ELECTRICAL DICTIONARY. 



487 



Soldering, Electric, -(a) Soldering in which the solder is 
melted by means of electricity ; either current incandescence or 
the voltaic arc may be used. It is identical in general with electric 
welding. (See Welding ', Electric.) 

(b) The deposition by electric plating of a metal over the ends of 
two conductors held in contact. This secures them as if by solder- 
ing. It is used in connecting the carbon filament of an incandescent 
lamp with the platinum wires that pass through the glass. Copper 
is the metal usually deposited. 

Solenoid. The ideal solenoid is a system of circular currents 
of uniform direction, equal, parallel, of equal diameter of circle, 
and with their centers lying on the same straight line, which line 
is perpendicular to their planes. 

The simple solenoid as constructed of wire, is a helical coil, of 
uniform diameter, so as to represent a cylinder. After completing 
the coil one end of the wire is bent back and carried through the 
centre of the coil, bringing thus both ends out at the same end. 




Experimental Solenoid. 



The object of doing this is to cause this straight return member to 
neutralize the longitudinal component of the helical turns. This 
it does approximately so as to cause the solenoid for its practical 
action to correspond with the ideal solenoid. 

Instead of carrying one end of the wire through the centre of the 
coil as just described, both ends may be bent back and brought 
together at the centre . 

A solenoid should always have this neutralization of the longi- 
tudinal component of the helices provided for ; otherwise it is not 
a true solenoid. 

Solenoids are used in experiments to represent magnets and to 



488 STANDARD ELECTRICAL DICTIONARY. 

study and illustrate their laws. When a current goes through 
them they acquire polarity, attract iron, develop lines of force and 
act in general like magnets. 

A solenoid is also denned as a coil of insulated wire whose length 
is not small as compared with its diameter. 

Sonometer, Hughes'. A sound measurer; a modification of a 
portion of Hughes' induction balance, used for testing the delicacy 
of the ear or for determining the relative intensity of sounds. (See 
Hughes^ Induction Balance.) It is the arrangement of three coils, 
two mounted one at each of the ends of a graduated bar, and the 
third one between them and free to slide back and forth thereon. 

Sonorescence. The property of producing sounds under the 
influence of momentary light radiations rapidly succeeding each 
other. It is the property utilized in the photophone, q. v. 

Sounder. In telegraphy an instrument consisting of an electro- 
magnet with armature attached to an oscillating bar, the range 
of whose movements is restricted by adjusting screws. The 
armature is drawn away from the magnet by a spring. When a 
current is sent through the magnet the armature is drawn towards 
the poles and produces a sound as the bar strikes a striking piece 
or second adjusting screw. When the current ceases the bar and 




Fig. 306. Morse Sounder. 

armature are drawn back, striking the first mentioned screw with a 
distinct sound, the back stroke. 
The sounder is used to receive Morse and analogous character 



STANDARD ELECTRICAL DICTIONARY. 489 

messages. The forward strokes correspond to the beginnings of 
the dots or dashes of the code, the back strokes to beginnings of 
the intervals. The distinction between dots and dashes is made 
by observing the interval between forward and back stroke. 

Various devices are used to increase the sound. Sometimes a 
resonance box is used on which the sounder is mounted. 

In practice sounders are generally placed on local circuits and 
are actuated by relays. 

Sound Reading. The art or method of receiving telegraph 
messages by ear. It is now universally used by all expert Morse 
operators. It can only be applied to telegraph systems producing 
audible sounds ; in some cases, as in needle telegraphy, it may be 
quite inapplicable. 

Space, Clearance. The space between faces of the pole pieces 
and the surface of the armature in a dynamo. It is really the air 
gap, but in calculating dynamo dimensions the thickness of the 
insulated copper wire windings of the commutator are counted in 
as part of the air gap, because copper is almost the same as air in 
impermeability. Clearance space is a mechanical factor ; the air 
gap is an electric or magnetic factor. 

Synonym — Inter-air Space. 

Space, Crookes' Dark. In an exhausted tube, through which 
an electric discharge is caused to pass, the space surrounding the 
negative electrode of the tube. This space is free from any lumin- 
ous effect, and by contrast with the light of the discharge appears 
dark. The vacuum may be made so high that the dark space fills 
the whole space between the electrodes. It is less for a less vacuum 
and varies for other factors, such as the temperature of the nega- 
tive electrode from which it originates, the kind of residual gas 
present, and the quality of the spark. 

Space, Faraday's Dark. The space in an exhausted tube 
between the luminous glows about the two electrodes. 

Space, Interferric. A term for the air-gap in a magnetic cir- 
cuit. It is etymologically more correct than air-gap, for the latter 
is often two-thirds or more filled with the insulating material and 
copper wire of the armature windings. (See Space, Clearance.) 

Spark Arrester. A screen of wire netting fitting around the 
carbons of an arc lamp above the globe to prevent the escape of 
sparks from the carbons. 

Spark Coil.' A coil for producing a spark from a source of com- 
paratively low electro-motive force. It consists of insulated wire 
wound round a core of soft iron, best a bundle of short pieces of 
wire. Such a coil may be eight inches long and three inches 



49Q STANDARD ELECTRICAL DICTIONARY. 

thick, and made of No. 18-20 copper wire, with a core one inch in 
diameter. On connecting a battery therewith and opening or 
closing the circuit, a spark is produced by self-induction, q. v. It 
is used for lighting gas. 

Spark, Duration of Electric. Wheatstone determined the 
duration of the spark given by a Ley den jar as 24^00 second. Fed- 
, dersen by interposing a tube of water 9 millimeters (.36 inch) long in 
its path found that it lasted yoVo second, and with one 180 millimeters 
(7.2 inches) long, \\%%^ second. Lucas and Cazin for a 5 millimeter 
(.2 inch) spark, with different numbers of Leyden jars, found the 
following : 

Number of jars. Duration of Spark. 

2 .000026 second 

4 .000041 ' ' 

6 .000045 " 

8 .000047 " 

The duration increases with the striking distance, and is inde- 
pendent of the diameter of the balls between which it is produced. 

Spark Gap. The space left between the ends of an electric 
resonator (see Resonator, Electric) across which the spark springs. 
Its size may be adjustable by a screw, something like the arrange- 
ment of screw calipers. 

Sparking. In dynamo-electric machines, the production of 
sparks at the commutator between the brushes and commutator 
sections. The sparks are often true voltaic arcs, and in all cases 
are injurious if in any quantity, wearing out the commutator and 
brushes. 

Sparking, Line or Points of Least. In a dynamo or electric 
motor the diameter of the commutator determining, or the points 
on the commutator marking the position of the brushes where the 
sparking is a minimum. Field magnets powerful in proportion to 
the armature are a preventative cause. The direction of the line 
fixes the angle of lead to be given to the brushes. 

Sparking, Resistance to. The resistance to disruptive dis- 
charge through its substance offered by a dielectric or insulator. It 
does not depend on its insulating qualities, but on its rigidity and 
strength. 

Spark, Length of. The length of the spark accompanying the 
disruptive discharge is counted as the distance from one electrode 
to the other in a straight line. It is longer for an increased poten- 
tial difference between the two electrodes. If the gas or air between 
the electrodes is exhausted the length increases, until the vacuum 
becomes too high, when the length begins to decrease, and for a 



STANDARD ELECTRICAL DICTIONARY. 491 

perfect vacuum no spark however small can be produced. The 
shape of the conductor which is discharged, the material of the 
electrodes, and the direction of the current are all factors affecting 
the length of spark producible. 

Spark Tube. A tube used as a gauge or test to determine when 
the exhaustion of the vacuum chamber or bulb of an incandescent 
lamp is sufficiently high. 

The interior of the tube is connected with the interior of the bulb 
or chamber of the lamps in process of exhaustion, and hence shares 
their degree of exhaustion. From time to time connections with 
an induction coil are made. When the exhaustion is carried far 
enough no discharge will take place through the vacuum. As long 
as the tube acts like a Geissler tube the exhaustion is not con- 
sidered perfect. 

Specific Heat of Electricity. The heat absorbed or given out 
by a fluid in passing from one temperature to another depends on 
its specific heat. In the Peltier and the Thomson effects, q. v., 
the electric current acts as the producer of a change of temperature, 
either an increase or decrease as the case may be. This suggests 
an absorption of and giving out of heat which amount of heat cor- 
responding to a current of known amount is determinable, and 
may be referred to any unit of quantity such as the coulomb. This 
or some equivalent definite quantity of heat it has been proposed 
(Sir William Thomson) to term the Specific Heat of Electricity. 

Spent Acid. Acid which has become exhausted. In a battery 
the acid becomes spent from combination with zinc. It also loses 
its depolarizing power, if it is a chromic acid solution or of that 
type, and then may be said to be spent. 

Spent Liquor. The liquor of a plating bath which has become 
exhausted from use, the metal it contained being all or partly 
deposited. 

Sphygmograph, Electric. An electric apparatus for recording 
the beat of the pulse, both as regards its rate and strength. 

Sphygmophone. An apparatus for examination of the pulse 
by the microphone and telephone. 

Spiders. Core-discs of a dynamo or motor armature are some- 
times perforated with a large central aperture, are fastened together 
with insulated bolts, and the whole mass is secured to the shaft 
by three- or four-armed spiders. These are like rimless wheels, the 
ends of their arms being secured to the hollow cylinder consti- 
tuting the armature core, and a central aperture in their hub 
receiving the shaft. 



492 STANDARD ELECTRICAL DICTIONARY. 

Spiral. This term is sometimes used instead of coil, as the 
primary spiral or secondary spiral of an induction coil or trans- 
former. 

Spiral Winding. The winding used on ring armatures. This 
may diagrammatically be represented by a spiral carried around 
the ring shaped core. With two field poles it gives two collecting 
points, positive and negative, with four field poles it gives four col- 
lecting points, alternately positive and negative. 

Splice Box. A box in which the splices in undergound cables 
and electric lines are contained. The splicing is generally done 
in the boxes with the cables in place. They may be two-way for 
straight lines, or be four- way for two side or lateral connections. 

Spluttering. A term applied to a sound sometimes produced 
in a voltaic arc, perhaps caused by impure or insufficiently baked 
electrodes. (Elihu Thomson.) 

Spring Control. Control of or giving the restitutive force to 
the needle of a galvanometer, core of a solenoid ammeter or moving 
part of any similar instrument by a spring. As an example see 
Ammeter, Ayrton^s. 

Spring Jack. An arrangement for effecting, at one insertion of 
a species of plug, the opening or breaking of a circuit and for 
the simultaneous connection to the terminals formed by the break- 
ing of two terminals of another system or loop. Thus let a line 
include in its circuit two springs pressing against each other, 




Fig. 307. Spring Jacks. 

thereby completing the circuit. If a plug or wedge of insulating 
material were inserted between the springs so as to press them 



STANDARD ELECTRICAL DICTIONARY. 493 

apart it would break the circuit and the whole would constitute a 
spring jack cut-out. If each side of the plug had a strip of brass 
or copper attached to it, and if the ends of another circuit were 
connected to these strips, then the insertion of the plug would 
throw the new line into the circuit of the other line. 

Spring Jack Cut=out. A cut-out, of the general construction 
of a spring jack, q. v., except that a simple insulating plug or 
wedge is used in place of the metal-faced wedge with its con- 
nections of the regular spring jack. The insertion of an insu- 
lating wedge opens the circuit, which on its removal is closed. 
The regular spring jack wedge will operate in the same way, if its 
connections are kept open. 

Spurious Voltage. The voltage in excess of that developed by a 
secondary battery which is required in the charging process. It is 
about .25 volt. 

Square Wire. Wire whose cross-section is a square. It has 
been used of iron for building up the cores of armatures for dyna- 
mos or motors, for which it is peculiarly suitable, and also of 
copper as a winding for armatures. 

Staggering, adj. When the brushes of a dynamo are set, one 
a little in advance of the other on the surface of the commutator, 
they are said to be set staggering. It is used to get over a break 
in the armature circuit. 

State, Electrotonic. A term expressing an abandoned theory. 
Faraday at one time proposed the theory that a wire had to be in 
the electrotonic state to produce electro-motive force by move- 
ment through an electric field. Any such idea was ultimately 
abandoned by Faraday. 

Static Breeze. The electric breeze obtained by the silent dis- 
charge of high tension electricity. 

Static Electricity. Electricity at rest or not in the current 
form ordinarily speaking. The term is not very definite and at 
any rate only expresses a difference in degree, not in kind. The 
recognition of the difference in degree has now to a great extent 
also disappeared. 

Station, Central. The building or place in which are placed 
electrical apparatus, steam engines and plant supplying a district 
with electric energy. 

Station, Distant. The place at the further end of a telegraph 
line, as referred to the home station. 

Station, Home. The end of a telegraph line where the operat- 
ors using the expression are working. 



494 STANDARD ELECTRICAL DICTIONARY. 

Station, Transforming. In alternating current distribution, a 
building or place where a number of transformers are worked, so 
that low potential or secondary circuits are distributed therefrom. 

Steel. A compound of iron with carbon. The carbon may range 
from a few hundredths of one per cent, up to two per cent. For 
magnets, tool steel drawn to a straw color or a little lower is good. 
All shaping and filing should be done before magnetization. 

Steeling. The deposition of iron on copper plates by electroly- 
sis. In electrotyping a thin deposit of iron is thus given the 
relief plates before printing from them. The deposit is very hard 
and exceedingly thin, so that it does not interfere with the per- 
fection of the impression in the printing process. As the iron 
becomes worn it can be dissolved off with hydrochloric acid, which 
does not dissolve the copper, and a new deposit can be given it. 
Thus the plate may last for an indefinite number of impressions. 

The iron bath may be prepared by immersing in a solution of 
ammonium chloride, two plates of iron, connected as anode and 
kathode in a circuit. One plate dissolves while hydrogen is given 
off from the other. The solution thus produced is used for a bath. 

The hardness of the deposit, which is really pure iron, gives the 
name of " steeling." 

Synonym — Acierage. 

St. Elmo's Fire. Luminous static discharge effects sometimes 
seen on objects elevated in the air. They are especially noticed on 
ships' masts. The sailors term them corpusants (holy bodies). 
They resemble tongues or globes of fire. 

Step=by=step Telegraphy. A system of telegraphy in which 
in the receiving instrument a hand is made to move step-by-step, 
with an escape movement around a dial. For each step there is a 
letter and the hand is made to stop at one or the other letter until 
the message is spelled out. (See Dial Telegraph.) 

Step=down. adj. A qualification applied to a converter or 
transformer in the alternating current distribution, indicating that 
it lowers potential difference and increases current from the 
secondary. 

Step=up. adj. The reverse of step-down ; a qualification of a 
transformer or converter indicating that it raises the potential and 
decreases the current in the secondary. 

Sticking. The adherence, after the current is cut off, of the 
armature to the poles of a magnet. In telegraphy it is a cause of 
annoyance and obstructs the working. It may, in telegraphy, be 
due to too weak a spring for drawing back the armature, or to im- 



STANDARD ELECTRICAL DICTIONARY. 495 

perfect breaking of the contact by the despatcher's key or by the 
receiver's relay. 

Stopping Off. In electroplating the prevention of deposition 
of the plating metal on any desired portions of the object. It is 
effected by varnishing the places where no coating is desired. An 
article can be plated with silver, stopped oif in any desired design, 
and the unvarnished portions may then be plated with gold in 
another bath. Various effects can be produced by such means. 

Storage Capacity. A term for the ampere-hours of electricity, 
which can be taken in current form from a storage battery. 

Storage of Electricity. Properly speaking electricity can only 
be stored statically or in static condensers, such as Leyden jars. 
The term has been popularly applied to the charging of secondary 
or storage batteries, in which there is really no such thing as a 
storage of electricity, but only a decomposition and opposite com- 
bination brought about, which leave the battery in a condition to 
give a current. 

Storms, Electric. Wide-spread magnetic and electric disturb- 
ances, involving the disturbance of the magnetic elements and 
other similar phenomena. (See Magnetic Storms.) 

Strain. The condition of a body when subjected to a stress. 
Various conseqences may ensue from strain in the way of disturb- 
ance of electric and other qualities of the body strained. 

Stratification Tube. A Geissler tube, q. v., for showing the 
stratification of the electric discharge through a high vacuum. 

The stratifications are greatly intensified by the presence of a little 
vapor of turpentine, alcohol, bisulphide of carbon and other sub- 
stances. 

Stray Field. In a dynamo or motor the portion of the field 
whose lines of force are not cut by the armature windings. 

Stray Power. The proportion of the energy wasted in driving 
a dynamo, lost through friction and other hurtful resistances. 

Streamlets, Current. A conception bearing the same relation 
to an electric current that lines of force do to a field of force ; ele- 
mentary currents. If evenly distributed the current is of uniform 
density ; if unevenly distributed, as in alternating currents, the 
current density varies in different parts of the cross section of the 
conductor. This evenness or unevenness may be referred to the 
number of streamlets per unit of area of cross-section. 

Stress. Force exercised upon a solid tending to distort it, or to 
produce a strain. 



496 STANDARD ELECTRICAL DICTIONARY. 

Stress, Dielectric. The condition of a dielectric when main- 
taining a charge ; its two extremities are in opposite states of 
polarity, or are under permanent potential difference. As the two 
opposite polarites tend to unite a condition of stress is implied in 
the medium which separates them. 

Stress, Electro=magnetic. The stress produced upon trans- 
parent substances in an electro-magnetic field of force. It is shown 
in the modified optical properties of glass and similar substances 
placed between the poles of a strong electro-magnet. 

Stress, Electrostatic. The stress produced upon substances in 
an electrostatic field of force ; the exact analogue of electro-mag- 
netic stress, and affecting transparent substances in the same general 
way. 

Striae, Electric. In Geissler tubes the light produced by the 
electric discharge is filled with striae, bright bands alternating with 
dark spaces ; these may be termed electric striae. 

Striking Distance. The distance that separates two conductors 
charged with electricity of different potential, when a spark starts 
between them. 

Striking Solution. In silver-plating a bath composed of a weak 
solution of silver cyanide with a large proportion of free potassium 
cyanide. It is used with a strong current and a large silver anode. 
This gives an instantaneous deposition of metallic silver over the 
surface of the article which goes to insure a perfect coating in the 
silver bath proper. After a few seconds in the striking solution, 
the article is at once removed to the plating bath. 

Stripping. The removal of electroplating from an object. It 
may be effected in several ways. An object whose plating is to be 
removed is placed in a plating bath of the solution of the metal with 
which it is coated. It is connected as the anode to the positive plate 
of the battery or corresponding terminal of the generator. A kath- 
ode connected to the other terminal being placed in the bath, the 
coating is dissolved by electrolytic action. Sometimes simple treat- 
ment with acid is employed. Different stripping baths are described 
under the heads of the different metals. 

S. U. Symbol or abbreviation for Siemens' Unit of Resistance. 
(See Resistance, Siemens" Unit of.) 

Sub=branch. A branch or lead of wire taken from a branch lead ; 
a term used in electric distribution. 

Sub=main. In electric distribution a conductor connected directly 
to a main ; a branch. 

Subway, Electric. A subterranean system of conduits for elec- 



STANDARD ELECTRICAL DICTIONARY. 497 

trie cables. As generally constructed in this country it includes 
manholes, q. v., at the street corners connected by ducts or pipes. 
These pipes are large enough to hold a cable. To introduce a cable 
into a duct, which latter may be two or three inches in diameter, 
and from two hundred to six or seven hundred feet long, a wire or 
rope is first passed through the duct. This is done by a set of short 
wooden rods with screws at the end so as to be screwed together. 
Each rod must be shorter than the diameter of the manhole. A rod 
is thrust in, another is screwed to it and thrust in, and thus a set 
of rods is made to extend as far as desired. In pulling them out a 
rope is attached and drawn through. This rope or a larger one is used 
in drawing the cable through the duct. A windlass is employed to 
draw the rope with cable attached through the ducts. 

Sulphating. In storage battery cells, the formation of a hard 
white basic lead sulphate, Pb 2 S0 5 . Its formation is due to over-ex- 
haustion of the cells. As long as the voltage is not allowed to fall 
below 1.90 volts per cell little of it forms. As it accumulates it is apt 
to drop off the plate and fall to the bottom, thus weakening the plate 
possibly, and depriving it of active material, and clogging up the 
cell. If it carries a film of metallic lead with it, there is danger of 
short circuiting the cell. 

The presence of some sodium sulphate in the solution is said to 
tend to prevent sulphating, or to diminish it. 

Sulphur Dioxide. A compound gas, S 2 ; composed of 

Sulphur, 32 
Oxygen, 32 
Molecular weight, 64 
Specific gravity, 2.21. 
It is a dielectric of about the same resistance as air. Its specific 
inductive capacity at atmospheric pressure is : 1.0037 (Ayrton). 
Synonyms — Sulphurous Acid — Sulphurous Acid Gas. 

Sunstroke, Electric. Exposure to the arc light sometimes pro- 
duces the effects observed in cases of sunstroke. It is said that, in 
the case of workmen at electric furnaces, these effects are very 
'noticeable. (See Prostration , Electric.) 

Supersaturated, adj. A liquid is supersaturated when it has 
dissolved a substance at a temperature favorable to its solubility 
and its temperature has been allowed to change, the liquid being 
kept free from agitation or access of air, provided crytallization 
or precipitation has not taken place. It expresses the state of a 
liquid when it holds in solution more than the normal quantity 
of any substance soluble in it. 

Surface. A galvanic battery is arranged in surface when all 



STANDARD ELECTRICAL DICTIONARY. 



the positive plates are connected together and all the negative 
plates are also connected. This makes it equivalent to one large 
cell, the surface of whose plates would be equal to the aggregate 
surface of the plates of the battery. It is also used as an adjective, 
as " a surface arrangement of battery." 

Surface Density. The relative quantity of an electric charge 
upon a surface. 

Surface, Equipotential. A surface over all of which the poten- 
tial is the same. In a general sense equipotential surfaces are 
given by planes or surfaces which cut lines of force at right angles 
thereto, or which are normal to lines of force. The conception 
applies to electrostatic and electro-magnetic fields of force, and for 
current conductors the planes normal to the direction of the cur- 
rent are equipotential surfaces. 

The contour of an equipotential surface of a field of force which 
is drawn or represented by delineations of its lines of force can be 
obtained by drawing a line normal thereto. This line will ordin- 
arily be more or less curved, and will be a locus of identical 
potentials. 

An electric equipotential surface may be described as electro- 
static, electro-magnetic, or magnetic ; or may be an equipotential 
surface of a current conductor. Besides these 
there are mechanical and physical equipotential 
surfaces, such as those of gravitation. 

Surface Leakage. Leakage of current from 
one part of an insulating material to another by 
the film of moisture or dirt on the surface. 

Suspension. This term is applied to methods 
of supporting galvanometer needles, balance 
beams, magnetic compass needles and similar 
objects which must be free to rotate. (See 
Suspension, Bifilar — Fibre and Spring Sus- 
pension — Fibre Suspension — Knife Edge 
Suspension — Pivot Suspension — Suspension, 
Is' Torsion. 



Suspension, Bifilar. Suspension by two 
vertical parallel fibres, as of a galvanometer 
needle. The restitution force is gravity, the 
torsion being comparatively slight and negli- 
gible. Leaving torsion out of account the resti- 
tution force is (a) proportional to the distance 
between the threads ; (b) inversely proportional to their length ; 

(c) proportional to weight of the needle or other object suspended ; 

(d) proportional to the angle of displacement. 



Fig. 308. Diagram 
of Bifilar Suspen- 
sion. 



STANDARD ELECTRICAL DICTIONARY. 



499 



Assume two masses A and B at the end of a weightless rod, 
suspended by the parallel cords a A, b B. Let the rod be rotated 
through an angle 0. Consider the cord a A. Its lower end is 
swung through the angle 0, as referred to the center O ; the cord 
is deflected from the vertical by an angle ip, such that a A tang i/> = 
O A 2 sin 0/2. The component of gravitation tending to restore 
A to A, acting towards A is equal to m g tan ip. Its moment 
around O is equal to (m g tan rp) X (O A cos. 0/2). The whole 
moment of the couple is 2 m g tan ip .0 A. Cos. 0/2 = 2 m g 
(O A 2 /a A) 2 sin. 0/2. Cos 0/2 = 2 m g\{0 A 2 !a A) sin 0. The 
moment of the restoring force is thus proportional to the sine of 
the angle of deflection, and the oscillations of such a system are 
approximately simple harmonic. (Daniell.) 

If the twisting is carried so far as to cause the threads to cross and 
come in contact with each other the suspension ceases to be a bifi- 
lar suspension, but assumes the nature of a torsional suspension. 

Swaging, Electric. Mechanical swaging in which the objects 
to be swaged are heated by an electric current as in electric welding. 

S. W. G. Abbreviation for Standard Wire Gauge. 

Switch. A device for opening and closing an electric circuit. 
A simple type is the ordinary telegrapher's switch. A bar of 
metal is mounted horizontally by a pivot at one end, so as to be 




Fig - . 309. Simple Switch. 

free to rotate through an arc of a circle. In one position its free 
end rests upon a stud of metal. One terminal of a circuit is attached 



500 STANDARD ELECTRICAL DICTIONARY. 

to its journal, the other to the stud. Resting on the stud it closes 
the circuit, in other positions it opens the circuit. 

Switch, Automatic. A switch opened and closed by the elec- 
tric current. It is used for lighting distant incandescent lamps. 
It includes one or two electro-magnets operated by two push 
buttons. In the usual arrangement one button is black and the 
other white, for extinguishing and lighting respectively. When 
the white button is pushed it causes a current to pass through one 
of the electro-magnets. This attracts its armature, thereby making 
a contact and throwing the lamps into the lighting circuit. Then 
they remain lighted until the black button is pressed. This excites 
the other magnet, which attracts its armature, breaks the contact 
and extinguishes the lights. 

The object of the automatic switch is to enable distant lamps to 
be lighted without the necessity of carrying the electric leads or 
wires to the place whence the lighting is to be done. A very small 
wire will carry enough current to operate the magnets, and open 
circuit batteries, such as Leclanche batteries, may be used as the 
source of current for the switch, but generally the lighting current 
is used for the purpose. 

A single magnet may do the work. When the lighting button 
is pressed the magnet is excited, attracts its armature and holds it 
attracted, until by pressing the black button the current is turned 
off from it. In this case the lighting current is used to excite the 
magnet. 

Switch Board. A board or tablet to which wires are led con- 
necting with cross bars or other switching devices, so as to enable 
connections among themselves or with other circuits to be made. 

Switch, Circuit Changing. A switch whose arm in its swing 
breaks one contact and swinging over makes another. It is em- 
ployed to change the connections of circuits from one dynamo to 
another. 

Synonyms — Changing Switch — Changing Over Switch. 

Switch, Double Break. A form of switch in which double 
contact pieces are provided to give a better contact. One form 
consists of a hinged bar whose end swings down between two pairs 
of springs. Both pairs are connected to one terminal, and the bar 
to the other terminal of a circuit. 

Switch, Double Pole. A heavy switch for central station 
work, that connects and disconnects two leads simultaneously. 

Switch, Feeder. A heavy switch, often of double contact 
type, for connecting and disconnecting feeders from bus bars in 
central stations. 



STANDARD ELECTRICAL DICTIONARY. 501 

Switch, Knife. A switch whose movable arm is a narrow, deep 
bar of copper or brass, and which in making contact is forced in 
edgew r ays between tw T o springs connected to one terminal. The 
bar is connected to the other terminal. 

Synonyms — Knife Break Switch — Knife Edge Switch. 

Switch, Multiple. A switch which in the swing of its bar con- 
nects one by one with a number of contacts so that ultimately the 
end of its bar is in contact with all at once. It is used to throw- 
lights in and out in succession, and it can, if the multiple contacts 
connect with resistances, make them operate as a rheostat. 

Switch, Pole Changing. A switch for changing the direction 
of the current in a circuit. 

Switch, Reversing. A switch, often of the plug type (see 
Plug Switch) for changing the direction of current passing through 
a galvanometer. 

Switch, Snap. A switch constructed to give a quick, sharp 
break. It has a spiral spring interposed between the handle and 
arm. As the handle is drawm back to open it the spring is first 
extended, tlie bar being held by the friction of the contacts, until 
the spring suddenly jerks it up, thus breaking the contact. 

Switch, Storage Battery Changing. A switch for changing 
storage battery connections from series to multiple and back again. 

Switch, Three Way. A switch, so constructed that by turning 
its handle connection can be made from one lead to either of tw T o 
other leads, and also so that connection can be completely cut off. 

Sympathetic Vibration. The establishment of periodic move- 
ment in one body by impulses of the same period communicated to 
it from another body in motion. Thus if tw T o tuning forks are of 
the same pitch and one is sounded the other will begin to sound 
by sympathy, the sound waves communicating the necessary 
periodic impulses to it. 

Sympathetic vibrations are utilized in harmonic telegraphy. 
(See Harmonic Receiver — Telegraph, Harmonic.) 

T. Symbol of time. 

Tailings, (a) In high speed transmission of telegraph signals by 
the automatic system, the definiteness of the signal marks is some- 
times interfered with by retardation. Wrong marks are thus pro- 
duced called tailings, (b) The prolongation of the current at the 
distant receiving station of a telegraph line due to the discharge of 
the line and to self-induction. 

Synonyms — Tailing — Tailing Current. 



502 



STANDARD ELECTRICAL DICTIONARY. 



Tamidine. Reduced nitrocellulose. Nitrocellulose is dissolved 
in a proper solvent and is obtained by evaporation as a translucent 
solid mass. By ammonium sulphide or other reagent it is reduced 
so as to be virtually cellulose. It is cut into shape for filaments of 
incandescent lamps, which shapes are carbonized and flashed. 

Tangent Law. In a galvanometer the tangents of the angles of 
deflection of the needle are proportional to the deflecting force — 

I. When the controlling force is unaltered in absolute magnitude 
and direction by the motion of the needle. 

II. When the deflecting force acts at right angles always to the 
controlling force. 

These conditions are usually secured by having the actuating 
coil through which the current passes flat and of large diameter 
compared to the length of the needle ; by using the uniform field 
of the earth as the control ; by having a short needle ; by placing 
the coil with its plane in the magnetic meridian. 

For best proportions of tangent galvanometer coils see Bobbins. 

Tangent Scale. An arc of a circle in which the number of 
graduations in any arc starting from zero are proportional to the 
tangent of the angle subtended by such arc. The system is for use 
with tangent galvanometers. Thus if for 45 ° a value of 100 is 
taken and marked on the scale then for the arc 26 33' 4- a value 
of 50 should be marked on the scale because such are the relative 
values of the tangents. 





j 


1 


2 


3 


Fig. 56. 
4 5 


6 


7 


8 


9 




















^D 


H 








y^K 












C 


A// 


^ 

















Fig. 310. Graphic Construction of. Tangent Scale. 

Thus the scale instead of being divided into degrees is divided into 
arcs of varying length, growing shorter as they are more distant 
from the zero point, of such length that the first division being 
subtended by a tangent of length 1, the first and second divisions 
added or taken together as one arc are subtended by a tangent of 
lengths, and so on. 



STANDARD ELECTRICAL DICTIONARY. 



503 



In the cut a simple method of graphically laying out a tangent 
scale is shown. In it Cis the centre of the arc, and //the radius 
running to the zero of the instrument. From C a circle is described 
and on H a vertical line tangent to the arc is erected. Taking any 
part of the tangent, as the length shown ending at D, it is divided 
into any number of equal parts. Radii of the circle are now 
drawn whose prolongations pass through the divisions on the tan- 
gent. These radii, where they intersect the arc of the circle, 
determine equal divisions of the tangent scale, w T hich, as is evident 
from the construction, are unequal angular divisions of the arc. 

Tanning, Electric. The tanning of hides in the manufacture of 
leather by the aid of electrolysis. A current of electricity is main- 
tained through the tanning vats in which regular tanning liquor is 
contained. Very extraordinary claims are made for the saving of time 
in the tanning process. What is ordinarily a process of several 
months, and sometimes of a year, is said to be reduced to one 
occupying a few days only. The action of electrolysis is the one 
relied on to explain the results. 

Tapper. The key used in single needle telegraph transmitters. 
It comprises two flat springs Z, E, each 
with a handle, normally pressed upward 
against one contact bar Z, and when pressed 
down by the operator making contact against 
a lower bar C when messages are to be trans- 
mitted. A double tapper, such as shown, is 
used for each instrument. 

Synonyms -Double Tapper Kev — Pedal 
Key. 

Target, Electric. A target registering or 
indicating electrically upon an annunciator 
the point of impact of each bullet. 

Taste, Galvanic. The effect produced 
upon the gustatory nerves by the passage of 
an electric current, or by the maintenance 
of potential difference between two portions 
of the tongue. It is very simply produced by 
placing a silver coin above, and a piece of 
zinc below the tongue, or the reverse, and 
touching their edges. A sour, peculiar taste 
is at once perceived. It cannot be due to any measurable quan- 
tity of current or of electrolytic decomposition, because the couple 
can do little more than establish a potential difference. With 
a strong current the taste becomes too strong tor comfort, and 
if on a telegraph line the extra currents produced by the signaling 
make the operation of tasting the current a very unpleasant one. It 




Fig. 311. Tapper. 



504 STANDARD ELECTRICAL DICTIONARY. 

is said that messages have been received in this way, the receiver 
placing one terminal of the line on his tongue, and a terminal 
attached to a grounded wire below it, and then receiving the Morse 
characters by taste. 

Teazer. Originally a fine wire coil wound on the field magnets of 
a dynamo in shunt with the regular winding to maintain the mag- 
netism. It was originally used in electroplating machines to 
prevent inversion of the magnetism , but has since developed into a 
component part of the winding of the compound dynamo. (See 
Dynamo, Compound.) 

Tee, Lead. A lead pipe of T shape used for connecting branches 
to electric cables. The tee is soldered by wiped joints to the lead 
sheathings of the cable and branches after the wires have been con- 
nected, and the junctions coated with insulating tape or cement, 
or both. 

It is sometimes made in two halves, and is known as a split tee. 

Telautograph. A telegraph for reproducing the hand- writing of 
the sender at the receiving end of the line. To save time a special 
spelling is sometimes used. 

Teleautograph. The special spelling used with the Tel-Auto- 
graph telegraph. 

Tele=barometer, Electric. A barometer with electric attachment 
for indicating or recording at a distance the barometric readings. 

Telegraph, ABC. This term is applied to alphabet telegraphs 
indicating the message by the movements of a pointer on a dial 
marked with the characters to be sent. In England the Wheatstone 
ABC system is much employed. 

Telegraph, Automatic. A telegraph system based on the 
operation of the transmitting instrument by a perforated strip of 
paper drawn through it. The perforations made by an apparatus 
termed a perforator, are so arranged as to give telegraphic characters 
of the Morse or International Code in the transmitting instrument. 
(See Perforator.) Bain in the year 1846 was the originator of the 
system. He punched a fillet of paper with dots and dashes, and 
drew it between two terminals of the line, thus sending over the 
line a corresponding series of short and long currents which were 
received by his chemical receiver. (See Chemical Receiver.) The 
method was not successful. Its modern development, the Wheat- 
stone Automatic Telegraph, is highly so. The perforated paper by 
its perforations controls the reciprocating movement of two rods, 
which pass through each hole in two rows, corresponding to the 
two rods respectively as the holes come opposite to the ends of the 
rods. The rods are kept constantly moving up and down. If 



STANDARD ELECTRICAL DICTIONARY. 



505 



imperforated paper is above them their upward motion is limited. 
This gives three positions for the rods, (a) both down, (6) one up and 
the other down, (c) both up. These positions of the rods work a pole 
changing key by which dots, spaces, and dashes are transmitted to 
the receiving instrument, which is an exceedingly delicate ink- 
printer. The latter can have its speed adjusted to receive from 
200 to 450 words per minute. 

Telegraph, Dial. A telegraph in which as receiver a dial in- 
strument is used. A pointer or index hand moves around a dial. 
The dial is marked with letters of the alphabet. The movements 
of the pointer are controlled by the transmitting operator at a 
distant station. He by the same actions moves a pointer on 
a duplicate instrument before him and the two are synchronized 
to give identical indications. Thus a message is spelled out 
letter by letter on both dials simultaneously. The motions of the 
index are generally produced by what is virtually a recoil escape- 
ment. The scape wheel is carried by the axle of the index, and 
a pallet or anchor is vibrated by an electro-magnet whose arma- 
ture is attached to the stem of the pallet. As the pallet is vibrated 
it turns the wheel and index one tooth for each single movement. 
There are as many teeth in the wheel as there are characters on the 
dial. The two instruments being in duplicate and synchronized, 
the pallets move exactly in unison, so that identical readings of 
the dials are given. The pallets may be moved by any kind of 




Fig. 312. Dial Telegraph. 

make and break mechanism, such as an ordinary telegraph key. 
The indexmoves by steps or jerks, so that the system is sometimes 
called step-by-step telegraphy. 

In the cut the make and break transmitter is shown at v z\ 
with its handle and contacts g and /. This mechanism sends impulses 



5 o6 STANDARD ELECTRICAL DICTIONARY. 

of current by F and Z to the receiving magnet a b. This attracts 
and releases its armature K from contact int<3 the position indi- 
cated by the dotted lines. This works the rocker n on the pin o y 
and actuates the double or anchor pawl s r, which turns the pallet 
or scrape wheel m. 

The system is dropping into disuse, being supplanted by the 
telephone. 

Synonym — Step-by-step Telegraph. 

Telegraph, Double Needle. A telegraph system in which the 
message is read by the motions of two vertical needles on the 
face of the instrument in front of the receiving operator. An 
identical instrument faces the transmitting operator. By two 
handles, one for each hand, the needles are caused by electric 
impulses to swing to right and to left so as to give a telegraphic 
code. It has been generally superseded by the single needle tele- 
graph. 

Telegraph, Duplex. A telegraph capable of transmitting simul- 
taneously two messages over one wire. The methods of effecting 
it are distinct from those of multiplex telegraphy. This term is 
used as a distinction from diode multiplex telegraphy, in which 
the work is done on other principles. There are two systems of 
duplex telegraphy, the differential and the bridge systems. 

Telegraph, Duplex Bridge. A system of duplex telegraphy 
employing the principle of the Wheatstone bridge. The other or 
differential system depends on equality or difference of currents ; 
the bridge method on equality or difference of potentials. The 
cut shows the system known as Steam's Plan. 

At the ends of the line wire are two cross connections like 
duplicate galvanometer connections in a Wheatstone bridge, each 
including a receiving relay. The rest of the connections are self- 
explanatory. 

When A depresses his key the current splits at the point indi- 
cating the beginning of the bridge. One portion goes through the 
line to B and to earth, the other goes to earth at A through the 
rheostats indicated by the corrugated lines. 

On reaching B's end the current divides at the cross-connection 
and part goes through the receiving relay shown in the center of 
that cross-connection. 

Thus if A sends to B or B to A it is without effect on the home 
receiving instrument. Now suppose that both simultaneously are 
sending in opposite directions. If the connections be studied 
it will be seen that every movement of the transmitting key will 
affect the balance of the distant or receiving end of the bridge and 
so its instrument will record the signals as they are sent. 



STANDARD ELECTRICAL DICTIONARY. 



507 



As shown in the cut the sending keys are on local circuits, and 
work what are known as duplex transmitters. These are instru- 
ments which send line signals without breaking the connection. 



LIN E 




Fig"- 3*3- Stearn's Plan of Duplex Bridge Telegraphy. 

In Stearn's plan condensers are introduced as shown. By this 
plan different receiving instruments can be used. The inventor 
once worked a Morse instrument at one end of the line, and a 
Hughes' instrument at the other end. 

Telegraph, Duplex, Differential. A system of duplex teleg- 
raphy employing the differential action of two exciting or magnet- 
izing coils. The general principles are the following. Suppose 
that at each of two stations, there is a magnet working as a sounder 
or relay. Each magnet is differentially wound, with two coils of 
opposite direction, of identical number of turns. 

When the sending key at a station A is depressed two exactly 
equal currents go through the magnet in opposite directions. 
One called the compensation current goes to the earth at the 
stations. The other called the line current goes through the line, 
through the line coil of the distant station B } thereby actuating the 
relay or sounder armature. 

The instrument of the sender A is unaffected because he is send- 
ing opposite and equal currents through its two coils. A special 
resistance is provided on the compensation circuit for keeping the 
currents exactly equal in effect. Nothing the sender at A does 
affects his own instrument. 

Now suppose B desires to telegraph back at the same time that 
A is telegraphing to his station. He works his key. This does 
not affect his own instrument except by sending the equal and 



5o8 



STANDARD ELECTRICAL DICTIONARY. 



opposite currents through its coils. When his key is depressed 
and A's key is untouched, he works A's receiving instrument. 

When A's key is depressed simultaneously with B's key, the 
two line currents are in opposition and neutralize each other. 
This throws out the balance in the instruments and both armatures 
are attracted by the compensation currents left free to act by the 
neutralization of the line currents. 




Fig. 314. Duplex Telegraph, Differential System 

Suppose that B is sending a dash, and it begins while A's key is 
raised. The line and compensation currents in B's receiving in- 
strument neutralize each other and no effect is produced, while 
A's receiving instrument begins to register or indicate a dash. 
Now suppose A starts to send a dash while B's is half over. He 
depresses his key. This sends the two opposite currents through 
his magnet. His line current neutralizes B's working current so 
that the compensation currents in both receiving instruments hold 
the armatures attracted for the two dashes. Meanwhile A's dash 
ends and he releases his key. At once his line current ceases to 
neutralize B's line current, his receiving instrument is actuated 
now by B's line current, while B's receiving instrument ceases to 
be actuated by the compensation current. 

Two assumptions are made in the above description. The line 
currents are assumed to be equal in strength and opposite in 
direction at each station. Neither of these is necessary. The line 
current received at a station is always weaker than the outgoing 
line current, and it is the preponderance of the compensation cur- 
rent over the partly neutralized line current that does the work. 
As this preponderance is very nearly equal to the line current 
received from the distant station, the signals are actuated by almost 
the same current, whether it is compensation or line current. 

Both line currents may coincide in direction. Then when the 



STANDARD ELECTRICAL DICTIONARY. 



509 



two keys are depressed, a line current of double strength goes 
through both receiving instruments and both work by preponder- 
ance of the double line* current over the compensation current. 
In other respects the operation is the same as before described. 




/~**py»\ 




1 / 



Fig- 3 J 5- Duplex Telegraph, Differential System. 

The cut shows a diagram of the operation of one end of the line. 
R and R are resistances, E and E are earth contacts, and the two 
circles show the magnet of the receiving instrument wound with 




Fig. 316. Differential Duplex Telegraph Connections. 

two coils in opposition. The battery and key are also shown. It 
also illustrates what happens if the key of the receiver is in the 
intermediate position breaking contact at both 1 and 2. The send- 
er's line current then goes through both coils of the receiving 
instrument magnet, but this time in series, and in coincident 
direction. This actuates the instrument as before. Owing to the 



510 STANDARD ELECTRICAL DICTIONARY. 

resistance only half the normal current passes, but this half goes 
through twice as many coils or turns as if the receiver's key was 
in either of the other two positions. 

In actual practice there are many refinements. To compensate 
for the varying resistance of the line a rheostat or resistance with 
sliding connection arm is connected in the compensation circuit 
so that the resistance can be instantly changed. As the electro- 
static capacity of the line varies sectional condensers are also con- 
nected in the compensation circuits. 

Telegraph, Facsimile. A telegraph for transmitting facsimiles 
of drawing or writing. The methods employed involve the syn- 
chronous rotation of two metallic cylinders, one at the transmit- 
ting end, the other at the receiving end. 

On the transmitter the design is drawn with non-conducting ink. 
A tracer presses upon the surface of each cylinder and a circuit is 
completed through the two contacts. In operation a sheet of 
chemically prepared paper is placed over the surface of the receiv- 
ing cylinder. The two cylinders are rotated in exact synchronism 
and the tracers are traversed longitudinally as the cylinders rotate. 
Thus a number of makes and breaks are produced by the transmit- 
ting cylinder, and on the receiving cylinder the chemicals in the 
paper are decomposed, producing marks on the paper exactly cor- 
responding to those on the transmitting cylinder. 

Synonyms — Autographic Telegraph — Pantelegraph}^. 

Telegraph, Harmonic Multiplex. A telegraph utilizing sym- 
pathetic vibration for the transmission of several messages at once 
over the same line. It is the invention of Elisha Gray. The 
transmitting instrument comprises a series of vibrating reeds or 
tuning-forks, each one of a different note, kept in vibration each 
by its own electro-magnet. Each fork is in its own circuit, and 
all unite with the main line so as to send over it a make and break 
current containing as many notes superimposed as there are tuning 
forks. At the other end of the line there are corresponding tuning 
forks, each with its own magnet. Each fork at this end picks up 
its own note from the makes and breaks on the main line, by the 
principle of sympathetic vibration. 

To each pair of operators a pair of forks of identical notes are 
assigned. As many messages can be transmitted simultaneously 
as there are pairs of forks or reeds. 

The movements of a telegraph key in circuit with one of the 
transmitting reeds sends signals of the Morse alphabet, which are 
picked out by the tuning fork of identical note at the other end of 
the line. 



STANDARD ELECTRICAL DICTIONARY. 



5ii 



Telegraph, Hughes'. A printing telegraph in very extensive 
use in continental Europe. Its general features are as follows : 

The instruments at each end of the line are identical. Each 
includes a key board like a piano manual, with a key for each letter 
or character. On each machine is a type wheel, which has the 
characters engraved in relief upon its face. With the wheel a 
" chariot " as it is termed also rotates. The type wheels at both 
stations are synchronized. When a key is depressed, a pin is thrown 
up which arrests the chariot, and sends a current to the distant 
station. This current causes a riband of paper to be pressed up 
against the face of both type wheels so as to receive the imprint of 
the character corresponding to the key. The faces of the wheels 
are inked by an inking roller. 




Fig. 317. Electro-magnet of Hughes' Printing Telegraph. 

The most characteristic feature is the fact that the current sent by 
depressing a key does not attract an armature, but releases one, 
which is then pulled back by a spring. The armature is restored to 
its position by the mechanical operation of the instrument. The 
magnet used is a polarized electro-magnet. Coils are carried on 
the ends of a strong powerful magnet. The coils are so connected 
that a current sent through them by depressing a key is in opposi- 
tion to the magnetism of the permanent magnet so that it tends to 
release the armature, and in practice does so. This release permits 
the printing mechanism to act The latter is driven by a descend- 
ing weight, so that very slight electric currents can actuate the 
instruments. 

Synonym — Hughes' Type Printer. 

Telegraphic Code, {a) The telegraphic alphabet, as of the 
Morse System. {See Alphabet, Telegraphic.) 

(5) A code for use in transmitting messages either secretly, or 
comprising several words or short sentences in one word, in order to 



512 



STANDARD ELECTRICAL DICTIONARY. 



economize in transmission, 
commercial cable messages. 



Such codes are extensively used in 



Telegraph, Magneto=eIectric. A telegraph in which the cur- 
rent is produced by magneto-electric generators. It has been applied 
to a considerable extent in England. The Wheatstone A B C or dial 
telegraph is operated by a magneto-generator turned by hand. 

In this country the magneto-electric generator by which the call- 
ing bell of a telephone is rung is an example. The magneto-electric 
key (See Key, Magneto-electric) is for use in one kind of mag- 
neto-electric telegraphing. 

Telegraph, Morse. A telegraph, characterized by the use of a 
relay, working a local circuit, which circuit contains a sounder, or 
recorder for giving dot and dash signals constituting the Morse 
alphabet. The signals are sent by a telegraph key, which when 
depressed closes the circuit, and when released opens it. The two 
underlying conceptions of the Morse Telegraph system are the use 
of the dot and dash alphabet, and the use of the local circuit, which 
circuit includes a receiving instrument, and is worked by a relay, 
actuating a local battery. It would be difficult to indicate any 
invention in telegraphy which has had such far-reaching conse- 
quences as the one known as the Morse telegraph. 

In other places the principal apparatus of the system will be found 
described. The cut Fig. 318, repeated here gives the general dis- 
position of a Morse system. (See Circuit, Local.) 




7 ^-..j 

-•^lflEMMi \. 



r 



Fig. 318. Diagram of Morse System. 

The key by which the messages are transmitted is shown in Fig. 
319. M \s a base plate of brass. A is a brass lever, mounted on an 
arbor G carried between -adjustable set screws D. C is the anvil 
where contact is made by depressing the key by the finger piece B 
of ebonite. E, F 1 are adjusting screws for regulating the vertical 



STANDARD ELECTRICAL DICTIONARY. 



play of the lever. H is the switch for opening or closing the cir- 
cuit. It is opened for transmission, and closed for receiving. By 
screws, L Z, with wing nuts, K K, the whole is screwed down to a 
table. 




Fig. 319. Morse Telegraph Key. 

In the United States the simplest disposition of apparatus is 
generally used. The main line is kept on closed circuit. In it may 
be included a large number of relays at stations all along the line, 
each with its own local circuit. There may be fifty of such stations. 
Battery is generally placed at each end of the line. Very generally 
gravity batteries are used, although dynamos now tend to supplant 
them in important stations. 

As relays the ordinary relay is used. Its local circuit includes a 
sounder and local battery. The latter is very generally of the 
gravity type, but oxide of copper batteries (See Battery, Oxide of 
Copper) are now being introduced. At main or central offices, the 
terminals of the lines reach switch boards, where by spring-jacks 
and plugs, any desired circuits can be looped into the main circuit 
in series therewith. 

In European practise the main line is kept on open circuit. Polar- 
ized relays are used to work the local circuits. The currents for 
these have to be alternating in direction. When the line is not in 
use its ends are connected to earth at both ends, leaving the battery 
out of circuit. Each intermediate station has its own main, or line 
battery for use when it desires to send a message. In the American 
system as first described, it will be seen that the main batteries are 
at most two in number. 



5 i4 STANDARD ELECTRICAL DICTIONARY. 

For the details of the different apparatus, the following definitions 
may be consulted: Embosser, Telegraphic — Recorder, Morse — 
Relay — Relay Connection — Sounder, 

Telegraph, Multiplex. A system of telegraphy by which a 
number of messages can be transmitted in both directions over a 
single wire. The principles underlying the systems are the fol- 
lowing : 

Suppose that at the two extremities of a telegraph line two arms 
are kept in absolute synchronous rotation. Let the arms in their 
rotation, press upon as many conducting segments as there are to 
be transmissions over the line. A transmitting and receiving set 
of instruments may be connected to one segment at one end of the 
line, and another set to the corresponding segment at the distant 
station. For each pair of segments two sets can be thus connected. 
Then if the arm rotates so rapidly that the contacts succeed each 
other rapidly enough each pair of sets of instruments can be worked 
independently of the others. In practice this rapid succession is 
effected by having a number of contacts made for each pair during 
a single rotation of the arm or equivalent. 

The multiplex system has been perfected by the use of La Cour's 
phonic wheel (see Phonic Wheel), and brought into a practical 
success by Patrick B. Delany, of New York. 

Two phonic wheels rotate at each end of the line. They are 
kept in synchronous motion by two vibrating steel reeds of exactly 
the same fundamental note, and the axle of each wheel carries an 
arm whose end trails over the contacts or distributor segments 
already spoken of. The reeds are adjusted to vibrate at such speed 
that the trailer is in contact with each segment about -g-Jo second. 
The number of groups of segments required for each working is 
determined by the retardation of the signals owing to the static 
capacity of the line. To convert the rapidly recurring impulses of 
current into practically a single current, condensers are connected 
across the coils of the relay. One battery serves for all the arms. 

Multiplex telegraphy can effect from two to six simultaneous 
transmissions over one wire. For two or four transmissions the 
method only distinguishes it from duplex or quadruplex telegraphy. 
The terms diode, triode, tetrode, pentode and hexode working are 
used to indicate respectively the simultaneous transmission of two, 
three, four, five, or six messages over one wire. 

It will be seen that the multiplex process really assigns to each 
transmission separate times, but divides these times into such short 
and quickly recurring intervals that the work is executed as if 
there was continuous contact. In no case is there the popular 
conception of the sending of several messages actually simultane- 
ously over one wire. Each signal in reality has its own time 



STANDARD ELECTRICAL DICTIONARY. 515 

assigned it, divided into short periods of high frequency, and only 
utilizes the line when it is free. 

Telegraph, Over=house. An English term for telegraph lines 
led over houses and supported on standards on the roofs. 

Telegraph Pole Brackets. Arms for carrying insulators, which 
arms are attached to telegraph poles or other support. They vary 
in style ; sometimes they are straight bars of wood gained into 
and bolted or spiked in place ; sometimes they are of iron. 

Telegraph, Printing. Various telegraphs have been invented 
for printing in the ordinary alphabet the messages at the receiving 
end of the line. 

Representative instruments of this class are used for transmitting 
different market and stock reports to business offices from the 
exchanges. The type faces are carried on the periphery of a 
printing wheel, which is rotated like the hand of a dial telegraph, and 
against whose face a paper riband is pressed whenever the proper 
letter comes opposite to it. As each letter is printed the paper 
moves forward the space of one letter. Spacing between words is 
also provided for. In the recent instruments two lines of letters 
are printed on the paper one above the other. 

In England, and on the continent of Europe, printing instru- 
ments have received considerable use for ordinary telegraphic 
work. Hughes' type printer and Wheatstone's ABC telegraph 
meet with extensive use there for ordinary transmission. 

Telegraph, Quadruplex. Duplex telegraphy is the sending of 
two messages in opposite directions simultaneously through the 
same wire. Duplex telegraphy is the sending of tw r o messages 
simultaneously in the same direction. The two combined consti- 
tute quadruplex telegraphy. 

The system was suggested by Stark of Vienna and Bosscha of 
Ley den in 1855 ; the successful problem was solved by Edison in 

l8 74- 

The principle is based on the two orders of difference in electric 
currents ; they may vary in strength or in direction. Thus we 
may have one instrument which works w T ith change of strength of 
current only, the other with change of direction only. The two 
can be w r orked together if the direction of the current can be altered 
without alteration of strength, and if strength can be altered with- 
out alteration of direction. Double current and single current 
working are so combined that one relay works by one system of 
currents and another relay by the other system. A current is con- 
stantly maintained through the line. The relay operated by 
change in direction is a simple polarized relay which works by 
change of direction of current. The relay operated by change in 
strength is the ordinary unpolarized relay. 



5i6 



STANDARD ELECTRICAL DICTIONARY. 



For the following description and the cuts illustrating it we are 
indebted to Preece and Sivewright. The cut shows the arrange- 
ment of the apparatus and connections for terminal offices. 

* ' Sufficient table room is provided to seat four clerks. The 
apparatus is arranged for the two senders to sit together in the 
centre, the messages to be forwarded being placed between them. 
The section on the left of the switch Q is known as the ' A ' side, 
that on the right as the ' B ' side of the apparatus. 

K x , the reversing key, reverses the direction of the current. K 2 
is a simple key, known as the increment key ; it is used simply to 
increase the strength of the current. 

The way in which the keys K x and K 2 combine their action is 
shown by Fig. 321. E Y and E 2 are the line batteries, the one hav- 
ing two and one-third (2^) the number of cells of the other, so 
that if E x be the electro-motive force of the smaller, that of the 



OOWN LINf . 




Fig. 320. Quadruplex Telegraph Connections. 

whole combined battery will be 3.3 E x . The negative pole of E l 
is connected to z and z x of K x , and the positive pole of E 2 to a of 
K 2 through a resistance coil s. A wire, called the ' tap ' wire, con- 
nects the positive pole of E x and the negative pole of E 2 to b of K 2 . 
This wire has in it a resistance coil r 2 . The springs c and c x of K x 
are connected to the lever L of K 2 . Now, when both keys are at 
rest, the negative pole of E x is to line through z, and the positive 
pole of E x to earth through b of K 2 and c of K Y ; the positive pole 



STANDARD ELECTRICAL DICTIONARY. 



517 



of E 2 being insulated at a of K 2 . There is thus a weak negative 
current flowing to line. When K Y alone is worked, the current of 
E Y is reversed. When K 2 is worked alone, c of K x is transferred 
from 5 to a, and the strength of the negative current going to line 
is increased through the increase of the electro-motive force from 
E\ t° 3-3 £i> f° r the whole battery is brought into play. When 
K x and K 2 are depressed together, then the negative pole of E Y 
goes to earth through z x ; and the positive pole of E 2 to line 
through a of K 2 and c x of K x , and a positive current, due to the 
whole electro-motive force 3.3 E } , goes to line. Hence the effect 
of working K x is simply to reverse the current, whatever its 
strength, while that of K 2 is to strengthen it, whatever its direction. 
The resistance coil s, of ioo° resistance, is called a spark coil, 
because it prevents the high electro-motive force of the whole 
battery from damaging the points of contact by sparking or forming 
an arc across when signals are sent ; and the resistance r 2 is made 
approximately equal to the combined resistance of E 2 and the 
spark coil, so that the total resistance of the circuit may not be 
altered by the working of the apparatus. 




Fig. 321. Quadruplex Telegraph. 

A Y and B l (Fig. 320) are the relays which are used to respond to 
the changes in the currents sent by the keys K Y and K 2 at the 
distant station. 

A Y is a simple polarized relay wound differentially, each wire 
having a resistance of 200 oj, and so connected up as to respond to 
the working of the reversing key K x of the distant station. It acts 
independently of the strength of the current, and is therefore not 
affected by the working of the increment key K 2 . It is connected 
up so as to complete the local circuit of the sounder S x and the 
local battery l lt and forms the receiving portion of the ' A ' side. 

B x is a non-polarized relay also wound differentially, each coil 
having a resistance of 200 go. It responds only to an increase in the 
strength of the current, and therefore only to the working of the 
increment kev K 2 of the distant station. 



518 STANDARD ELECTRICAL DICTIONARY. 

The relay spring is so adjusted that the armatures are not 
actuated by the weak current sent from E by the key K x . 

In its normal position this relay completes the circuit of the 
local battery through the sounder .S*. This sounder S, called the 
uprighting sounder, acts as a relay to a second sounder, kS^, called 
the reading sounder, which is worked by another local battery, / 2 . 
Of course, normally, the armature of ^is held down and that of kS" 2 
is up, but when the tongue t moves, as it does when the increment 
key A" 2 is depressed so as to send the whole current to line, then 
th.e current from / is interrupted, and the circuit of / 2 is completed 
by the rising of the armature of S, causing the reading sounder S 2 
to work. This is the ' B ' side. 

R is a rheostat for balancine the resistance of the line, as used in 
duplex working. 

C is a condenser used for compensating the static charge of the 
line. It is provided with an adjustable retardation coil, R ly to pro- 
long the effect of the compensating current from the condenser. 

G is a differential galvanometer, used for testing, and for facili- 
tating adjustment and balancing. 

Q is a switch for putting the line to earth, either for balancing, 
or for any other purpose. There is on the earth wire leading from 
Q a resistance coil, r 1} equalling approximately the resistance of 
the whole battery, 3.3 E x , and the resistance s. 

The connections shown in Fig. 321, are for an ' up ' office. At 
a ' down ' office it is necessary to reverse the wires on the two lower 
terminals of the galvanometer and the two battery wires on the 
reversing key K Y . 

The keys K x and K 2 are, for repeaters, replaced by transmitters. 

The adjustment of this apparatus requires great care and great 
accuracy. Its good working depends essentially on technical skill 
that can only be acquired by patience and perseverance. 

Faults in working generally arise from careless adjustments, 
dirty contacts, loose connections, battery failures, and the ordinary 
line interruptions, but there are no troubles that are beyond the 
reach of ordinary skill, and it can be safely said that, within mod- 
erate distances, wherever and whenever duplex working is practic- 
able, then quadruplex working is so too." 

The above is a typical quadruplex bridge system. There is also 
a differential system, the full description of which, in addition to 
what has been given, is outside of the scope of this work. 

Telegraph Repeater. An extension of the relay system, adopted 



STANDARD ELECTRICAL DICTIONARY. 519 

for long lines. A repeating station comprises in general terms 
duplicate repeating apparatus. One set is connected for messages 
in one direction, the other for messages in the opposite direction. 
The general operation of a repeating set is as follows. The signals 
as received actuate a relay which by its local circuit actuates a 
key, which in ordinary practise would be the sounder, but in the 
repeater its lever opens and closes a circuit comprising a battery 
and a further section of the line. 

Repeaters are placed at intervals along the line. Each repeater 
repeats the signals received for the next section of line with a 
new battery. It represents an operator who would receive and 
repeat the message, except that it works automatically. 

The Indo-European line from London to Teheran, 3,800 miles 
long, is worked directly without any hand retransmission, it being 
carried out by five repeaters. This gives an average of over 500 
miles for each repeater. 

Repeaters introduce retardation, and each repeater involves a 
reduction in the rate of working. Yet in many cases they increase 
the speed of a line greatly, as its speed is about equal to that of its 
worst section, which may be far greater than that of the whole 
line in one. 

Synonym — Translater. 

Telegraph Signal. In the telegraph alphabet, a dot, or dash ; 
the signal or effect produced by one closing of the circuit. A 
dash is equal in length to three dots. The space between signals is 
equal to one dot ; the space between letters to three dots ; and the 
space between words to six dots. 

Telegraph, Single Needle. A telegraph system in which the 
code is transmitted by the movements of a needle shaped index 
which oscillates to right and left, the left hand deflection corre- 
sponding to dots, the right hand deflection to dashes. The instru- 
ments for sending and receiving are combined into one. The 
needles are virtually the indexes of vertical galvanometers. In one 
form by a tapper key (see Tapper), in another form by a key 
worked by a drop-handle (the drop handle instrument), currents 
of opposite directions are sent down the line. These pass through 
both instruments, affecting both needles and causing them to 
swing to right or left, as the operator moves his key. 

As galvanometer needle or actuating needle a soft iron needle 
is employed, which is polarized by the proximity of two perma- 
nent magnets. This avoids danger of reversal of polarity from 
lightning, a trouble incident to the old system. 



520 



STANDARD ELECTRICAL DICTIONARY. 



The cut, Fig. 322, shows a single needle telegraph instrument 
of the tapper form. The action of the tapper can be understood 
from the next cut. 

Cand Z are two strips of metal to which the positive and nega- 
tive poles of the battery are respectively connected. E and L are 
two metallic springs ; E is connected to earth, L is connected to the 





Fig. 322. 



Single Needle Telegraph Instrument, 
Double Tapper Form. 



Fig. 323. Double Tapper 
Key for Single Needle 
Telegraph. 



line ; at rest both press against Z. If L is depressed so as to touch 
C y the current from the battery goes to the line by the key Z, goes 
through the coils of the distant instrument and deflects the needle 
to one side, and then goes to the earth. If the key E is depressed, 
L retaining its normal position, the direction of the current is 
reversed, for the other pole of the battery is connected to the earth, 
and the reverse current going through the coils of the distant 
instrument deflects the galvanometer needle to the other side. 



STANDARD ELECTRICAL DICTIONARY. 521 

In the drop-handle type an analogous form of commutator 
worked by a single handle produces the same effects. 

Telegraph, Wheatstone, A. B. C. A magneto-electric tele- 
graph of the dial system. An alternating current magneto-genera- 
tor is turned by hand and by depressing keys its current is admitted 
to or cut off from the line and receiver's instrument. The message 
is received by a dial instrument working by the escapement motion 
described under Telegraph, Dial. 

Telegraph, Writing. A telegraph in which the message is re- 
ceived in written characters. The transmitter includes a stylus 
which is held in the hand and whose point bears against the upper 
end of a vertical rod. The rod is susceptible of oscillation in all 
directions, having at its base a spring support equivalent to a uni- 
versal joint. 

The stylus is moved about in the shape of letters. As it does 
this it throws a series of resistances in and out of the circuit. 

At the receiving end of the line the instrument for recording 
the message includes two electro-magnets with their cores at right 
angles to each other and their faces near together at the point of 
the angle. An armature is supported between the faces and 
through it a vertical rod carried by a spring at its bottom rises. 
These magnets receive current proportional to the resistances cut 
in and out by the motions of the other rod at the transmitting end 
of the line. These resistances are arranged in two series at right 
angles to each other, one for each magnet. Thus the movements 
of the transmitting stylus and rod are repeated by the end of the 
rod in the receiving instrument. A species of pen is carried at 
the end of the rod of the receiving instrument, which marks the 
letters upon a riband of paper which is fed beneath it. 

Telemanometer, Electric. A pressure gauge with electric 
attachment for indicating or recording its indications at a distance. 

It is applicable to steam boilers, so as to give the steam pressure 
in any desired place. 

Telemeter, Electric. An apparatus for electrically indicating 
or recording at a distance the indications of any instrument such 
as a pressure gauge, barometer or thermometer, or for similar 
work. The telemanometer applied to a boiler conies into this class 
of instrument. 

Telephotography. The transmission of pictures by the electric 
current, the requisite changes in the current being effected by the 
action of light upon selenium. The picture is projected by a magic 
lantern. Its projection is traversed by a selenium resistance 
through which the current passes. This is moved systematically 
over its entire area, thus constituting the transmitter, and syn- 



522 STANDARD ELECTRICAL DICTIONARY. 

chronously with the motion of the selenium a contact point at the 
other end of the line moves systematically over a sheet of chemic- 
ally prepared paper. The paper, which may be saturated with a 
solution of potassium ferrocyanide and ammonium nitrate, is 
stained by the passage of the current, and by the variation in 
intensity of staining, which variation is due to variations in the 
current, produced by the effects of the light upon the selenium, 
the picture is reproduced. 

Telepherage. An electric transportation system, hitherto only 
used for the carrying of ore, freight, etc. Its characteristic feature 
is that the electric conductors, suspended from poles, supply the 
way on which carriages provided with electric motors run. The 
motors take their current directly from the conductors. 

There are two conducting lines, running parallel with each other, 
supported at the opposite ends of transverse brackets on a row of 
supporting poles. At each pole the lines cross over so that right 
line alternates with left, between consecutive pairs of poles. 

The cars are suspended from pulleys running on one or the other 
of the conductors. A train of such cars are connected and the cur- 
rent is taken in near one end and leaves near the other end of the 
train. These current connections are so distant, their distance 
being regulated by the length of the train, that they are, for all but 
an instant at the time of passing each of the poles, in connection 
with segments of the line which are of opposite potential. To 
carry out this principle the distance between contacts is equal to 
the distance between poles. Owing to the crossing over of the 
lines the contacts are in connection as described and thereby the 
actuating current is caused to go through the motors. 

Cars running in one direction go on the electric conductors on 
the one side, those running in the other direction go on the other 
conductor. 

A great many refinements have been introduced, but the system 
has been very little used. 

Telephone. An instrument for the transmission of articulate 
speech by the electric current. The current is defined as of the 
undulatory type. (See Current, Undulatory.) 

The cut shows what may be termed the fundamental telephone 
circuit. A line wire is shown terminating in ground plates and 
with a telephone in circuit at each end. The latter consists of a 
magnet N S with a coil of insulated wire //surrounding one end. 
Facing the pole of the magnet is a soft iron diaphragm D y held in 
a frame or mouthpiece T. Any change of current in the line 
affects the magnetism of the magnet, causing it to attract the dia- 
phragm more or less. The magnet and diaphragm really consti- 
tute a little electric motor, the diaphragm vibrating back and 



STANDARD ELECTRICAL DICTIONARY. 



523 



forth through an exceedingly short range, for changes in the mag- 
netic attraction. 

The principle of the reversibility of the dynamo applies here. 
If the magnet is subjected to no change in magnetism, and if the 
diaphragm is moved or vibrated in front of its poles, currents will 
be induced in the wire bobbin which surrounds its end. If two 
such magnets with bobbins and diaphragms are arranged as shown, 
vibrations imparted to one diaphragm will send currents through 
the line which, affecting the magnetism of the distant magnet, will 




£. 




Fig. 324. Diagram of Bell Telephones and Line with Earth Connections. 

cause its diaphragm to vibrate in exact accordance with the motions 
of the first or motor diaphragm. In the combination one telephone 
represents a dynamo, the other a motor. 

If the vibrations of the diaphragm are imparted by the voice, the 
voice with all its modulations will be reproduced by the telephone 
at the distant end of the line. 

The above gives the essential features of the Bell telephone. In 
practice the telephone is used only as the receiver. As transmitter 
a microphone is employed. To give the current a battery, generally 




Fig. 325. Section of Bell Telephone. 
of the open circuit type, is used, and the current in the line is an 
induced or secondarv one. 



524 



STANDARD ELECTRICAL DICTIONARY. 



The microphone which is talked to, and which is the seat of the 
current variations which reproduce original sound, is termed the 
transmitter, the telephone in which the sounds are produced at the 
distant end of the line is termed the receiver. 

Fig. 325 shows the construction of the Bell telephone in universal 
use in this country as the receiver. M is a bar magnet, in a case 
L L. B B is a bobbin or coil of insulated wire surrounding one 
end of the magnet. D is the diaphragm of soft iron plate (ferro- 
type metal), and E is the mouthpiece. The terminals of the coil 
B B connect with the binding screws CC. The wire in the coil 
is No. 36, A. W. G., and is wound to a 
resistance of about 80 ohms. 

As typical transmitter the Blake instru- 
ment may be cited. It is a carbon micro- 
phone. It is shown in section in the cut ; 
a is the mouthpiece and e is a diaphragm 
of iron plate, although other substances 
could be used \f is a steel spring, with a 
platinum contact piece at its end. One end 
bears against the diaphragm, the other 
against a carbon block k. The latter is car- 
ried by a brass block />, and pressure is 
maintained between these contacts by the 
spring g and weight of the piece c y which 
by gravity tends to press all together. 
The current passes by way of the spring 
y, carbon button k and spring g through 
the circuit indicated. 

A battery is in circuit with these parts. 
If a telephone is also in circuit, and the 
transmitter is spoken against, the dia- 
phragm vibrating affects the resistance of 
the carbon-platinum contact, without even 
breaking the contact, and the telephone 
reproduces the sound. The heavy piece 
of metal c acts by its inertia to prevent 
breaking of the contact. The position of 
this piece c, which is carried by the brass 

plate 7/z, is adjusted by the screw n. 

In practice the transmitter and battery are usually on a local 

circuit, which includes the primary of an induction coil. The line 

and distant receiving telephone are in circuit with the secondary 

of the induction coil, without any battery. 

Telephone, Bi=. A pair of telephones carried at the ends of a 
curved bar or spring so that they fit the head of a person using 




Fig. 326. Section of 
Blake Transmitter. 



STANDARD ELECTRICAL DICTIONARY. 5?5 

them. One telephone is held against each ear without the use of 
the hands. 

Telephone, Capillary. A telephone utilizing electro-capillarity 
for the production of telephonic effects. The following describes 
the invention of Antoine Breguet. 





Fig. 327. Breguet's Capillary Telephone. 

The point of a glass tube, drawn out at its lower end to a capillary 
opening dips vertically into a vessel. This vessel is partly rilled 
with mercury, over which is a layer of dilute sulphuric acid. The 
end of the immersed tube dips into the acid, but does not reach 
the mercury. One line contact is with mercury in the tube, 
the other with the mercury in the vessel. The arrangement of 
tube and vessel is duplicated, giving one set for each end of the 
line. On introducing a battery in the circuit the level of the mer- 
cury is affected by electro-capillarity. The tubes are closed by 
plates or diaphragms at their tops, so as to enclose a column 
of air. It is evident that the pressure of this air will depend 
upon the level of the mercury in the tube, and this depends on the 
electro-motive force. On speaking against the diaphragm the 
sound waves affect the air pressure, and consequently the level, 
enough to cause potential differences which reproduce the sound in 
the other instrument. 

Telephone, Carbon. A telephone transmitter based on the use 
of carbon as a material whose resistance is varied by the degree of 
pressure brought to bear upon it. L^ndoubtedly the surface contact 
between the carbon and the other conducting material has much to 
do with the action. Many carbon telephones have been invented. 
Under Telephone the Blake transmitter is described, which is a 
carbon telephone transmitter. The Edison carbon transmitter is 
shown in section in the cut. E is the mouth piece and D the 
diaphragm. / is a carbon disc with adjusting screw V. A platinum 
plate B B, with ivory button b, is attached to the upper surface of 
the carbon disc. C C is an insulating ring. The wire connections 



526 



STANDARD ELECTRICAL DICTIONARY. 



shown bring the disc into circuit. It is connected like a Blake 
transmitter. It is now but little used. 




Fig. 328. Section of Edison Carbon Transmitter. 

Telephone, Chemical. A telephone utilizing chemical or elec- 
trolytic action in transmitting or receiving. The electro-motograph 
is an example of a chemical receiver. (See Electro-motograph .) 

Telephone, Electrostatic. A telephone utilizing electrostatic 
disturbances for reproduction of the voice. In the cut D and C 



UNE 



m 



OQ 



Fig. 329. Diagram of Edison's Electrostatic Telephone. 

are highly charged electrophori. The diaphragms A and B 

when spoken to affect the potential of the electrophorus so as to 
produce current variations which will reproduce the sound. Dol- 
bear and others have invented other forms of transmitters based on 
electrostatic action. Receivers have also been constructed. A 
simple condenser may be made to reproduce sound by being con- 
nected with a powerful telephone current. 

Telephone Induction Coil. The induction coil used in tele- 
phone circuits for inducing current on the main line. It is simply 
a small coil wound with two separate circuits of insulated wire. 



STANDARD ELECTRICAL DICTIONARY. 527 

In the Edison telephone the primary coil, in circuit with the trans- 
mitter, is of No. 18 to 24 wire and of 3 to 4 ohms resistance. The 
secondary in circuit with the line and receiving instrument is of 
No. 36 wire and of 250 ohms resistance. The Bell telephone in- 
duction coil has its primary of No. 18 to 24 wire wound to a resist- 
ance of l /z ohm, and its secondary of No. 36 wire, and of 80 ohms 
resistance. 

Telephone, Reaction. A form of telephone containing two 
coils of insulated wire, one of which is mounted on the disc, and 
the other on the magnet pole in the usual way. These coils react 
upon each other so as to strengthen the effect. 

Telephone, Thermo=electric. A telephone transmitter in- 
cluding a thermo-electric battery, placed in circuit with the line. 
A plate of vulcanite faces it. When the sound waves strike the 
vulcanite they move it backward and forward. These movements, 
owing to the elasticity of the vulcanite, produce minute changes of 
temperature in it, which affecting the thermo-electric pile produce 
in the circuit currents, which passing through a Bell telephone cause 
it to speak. This type of instrument has never been adopted in 
practice. 

Telephote. An apparatus for transmitting pictures electrically, 
the properties of selenium being utilized for the purpose. 
Synonym — Pherope. 

Teleseme. An annunciator, displaying on a dial the object 
wanted by the person using it. It is employed to transmit messages 
from rooms in a hotel to the office, or for similar functions. 

Tele=thermometer. A thermometer with electric attachment 
for indicating or recording its indications at a distance. 

Tempering, Electric. A process of tempering metals by elec- 
trically produced heat. The article is made part of an electric cir- 
cuit. The current passing through it heats it, thereby tempering it. 
For wire the process can be made continuous. The wire is fed 
from one roll to another, and if required one roll may be immersed 
in a liquid bath or the wire between the rolls may be led therein. 
The current is brought to one roll and goes through the wire to 
the other. As it does this the wire is constantly fed from one roll 
to another. The bath may be used as described to cool it after the 
heating. The amount of heating may be regulated by the rate of 
motion of the wire. 

Ten, Powers of. This adjunct to calculations has become al- 
most indispensable in working with units of the C. G. S. sys- 
tem. It consists in using some power of 10 as a multiplier which 



528 STANDARD ELECTRICAL DICTIONARY. 

may be called the factor. The number multiplied may be called 
the characteristic. The following are the general principles. 

The power of 10 is shown by an exponent which indicates the 
number of ciphers in the multiplier. Thus io 2 indicates ioo ; io 3 
indicates 1,000 and so on. 

The exponent, if positive, denotes an integral number, as shown 
in the preceding paragraph. The exponent, if negative, denotes 
the reciprocal of the indicated power of io. Thus io- 2 indicates 
yJo ; io- 3 indicates TI ^ and so on. 

The compound numbers based on these are reduced by multi- 
plication or division to simple expressions. Thus: 3.14 X io 7 = 
3.14 x 10,000,000 = 31,400,000. 3.14 X 10 7 = T (jfeVooo or 
roowrrWoo* Regard must be paid to the decimal point as is 
done here. 

To add two or more expressions in this notation if the exponents 
of the factors are alike in all respects, add the characteristics and 
preserve the same factor. Thus : 

(51 X io 6 ) + (54 X io 6 ) = 105 X io 6 . 

(9.1 X io- 9 ) + (8.7 X io- 9 ) = 17.8 X io- 9 . 

To subtract one such expression from another, subtract the char- 
acteristics and preserve the same factor. Thus : 

(54 X io 6 ) — (51 X io 6 ) =3 X io 6 . 

If the factors have different exponents of the same sign the factor 
or factors of larger exponent must be reduced to the smaller ex- 
ponent, by factoring. The characteristic of the expression thus 
treated is multiplied by the odd factor. This gives a new expression 
whose characteristic is added to the other, and the factor of smaller 
exponent is preserved for both, 

Thus: 

(5 X io 7 ) + (5 X io 9 ) = (5 X io 7 ) + (5 X 100 X io 7 ) = 505 X 
io 7 . 

The same applies to subtraction. Thus : 

(5 X io 9 ) — (5 X io 7 ) == (5 X 100 X io 7 )— (5 X io 7 ) = 495 X io 7 . 

If the factors differ in sign, it is generally best to leave the 
addition or subtraction to be simply expressed. However, by fol- 
lowing the above rule, it can be done. Thus : 

Add 5 X io- 2 and 5 X io 3 . (5 X io 3 .) 

5 X io 3 =5 X io 5 X io- 2 ; (5 X io 5 X io- 2 ) + (5 X io- 2 ) = 500005 
X io- 2 . This may be reduced to a fraction --° r °o™- = 5000.05. 

To multiply add the exponents of the factors, for the new factor, 
and multiply the characteristics for a new characteristic. The ex- 



STANDARD ELECTRICAL DICTIONARY. 529 

ponentsmustbe added algebraically: that is, if of different signs 
the numerically smaller one is subtracted from the other one, and 
its sign is given the new exponent. 
Thus : 

(25 X io 6 ) X (9 X io 8 ) = 225 X io u . 
(29 X io- 8 ) X (11 X io 7 ) == 319 X io- 1 . 
(9 X io 8 ) X (98 Xio 2 ) = 882 X io 10 . 
To divide, subtract (algebraically) the exponent of the divisor 
from that of the dividend for the exponent of the new factor, and 
divide the characteristics one by the other for the new character- 
istic. Algebraic subtraction is effected by changing the sign of the 
subtrahend, subtracting the numerically smaller number from the 
larger, and giving the result the sign of the larger number. (Thus 
to subtract 7 from 5 proceed thus : 5 — 7 = — 2.) 
Thus: 

(25 X io 6 ) — (5 X io 8 ) =5 X io- 2 

(28 X IO- 8 ) ^r (5 X IO 3 ) = 5.6 X IO- 11 

Tension. Electro-motive force or potential difference in a cur- 
rent system is often thus termed. It is to be distinguished from 
intensity or current strength, which word it too greatly resembles. 

Tension, Electric, (a) The condition an electrified body is 
brought into by electrification, when each molecule repels its 
neighbor. The condition is described as one of self-repulsion. 

(b) The voltage or potential difference of a circuit is also thus 
termed. 

Terminal. The end of any open electric circuit, or of any 
electric apparatus ; as the terminals of a circuit, dynamo, or battery. 

Terminal Pole. In telegraph line construction the last pole of 
a series ; one beyond which the line is not carried. Such pole, as 
the pull of the wires is all in one direction, requires special staying 
or support. The regular line poles are free from this strain, as the 
wire pulls in both directions. 

Tetanus, Acoustic. A term in electro-therapeutics. An effect 
produced on a nerve by very rapidly alternating induced currents. 
The currents are produced by an induction coil with a vibrator 
giving a musical note. This is a species of gauge of proper fre- 
quency of alternations. 

Theatrophone. An apparatus worked by automatic paying 
machinery by which a telephone connection is made with a theatre 
or opera by the deposition of a coin in a slot. 

Therm. A unit of heat. It has been proposed by the British 
Association and amounts to a redefinition of the smaller calorie. It 



530 STANDARD ELECTRICAL DICTIONARY. 

is the amount of heat required to raise the temperature of one gram 
of water one degree centigrade, starting at the temperature of 
maximum density of water. 

Thermaesthesiometer. An electro-therapeutic instrument for 
testing the sensitiveness of the surface of the body to changes of 
temperature. Vessels of mercury are provided with thermometers 
to indicate their temperature. One vessel is surrounded by an 
electric conductor wound in a number of turns. The temperature 
is raised by passing a current through this. By successive appli- 
cations of the vessels to the same spot upon the skin the power of 
differentiating temperatures is determined. 

Thermo Call, (a) An electric alarm or call bell operated by 
thermo-electric currents. It may serve as a fire alarm or heat indi- 
cator, always bearing in mind the fact that differential heat is the 
requisite in a thermo-electric couple. 

(b) See Thermo-electric Call. 

Thermo=chemical Battery. A voltaic battery in which the 
electro-motive force is generated by chemical action induced by 
heat. 

The chemical used generally is sodium nitrate or potassium 
nitrate. The positive plate is carbon. On heating the battery the 
nitrate attacks the carbon, burning it and produces potential differ- 
ence. For negative plate some metal unattacked by the nitrate 
may be employed. 




Fig". 330. Pouillet's Thermo-electric Battery. 

Thermo=electric Battery or Pile. A number of thermo-electric 
couples q. v., connected generally in series. 

In Nobili's pile the metals are bismuth and antimony ; paper 



STANDARD ELECTRICAL DICTIONARY. 



531 



bands covered with varnish are used to insulate where required. 
In Becquerel's pile copper sulphide (artificial) and German silver, 
(90 copper, 10 nickel) are the two elements. The artificial copper 
sulphide is made into slabs 4 inches long, % inch wide, and y z inch 
thick (about). Water is used to keep one set of junctions cool, and 




Fig". 331. Becquerel's Thermo-Electrjc Batteries. 

gas flames to heat the other set. In Fig. 331, r, ^ represent the bind- 
ing screws. The couples are mounted on a vertical standard, with 
adjusting socket and screw B, so that its lower end can be im- 
mersed in cold water, or raised therefrom as desired. 

Fig. 332 shows one couple of the battery. 6* is artificial anti- 
mony sulphide ; M is German silver ; in is a 
protecting plate of German silver to save 
the sulphide from wasting in the flame. 

Clamond's pile has been used in practical 
work. The negative element is an alloy of 
antimony, 2 parts, zinc, 1 part. The positive 
element is tin plate. Mica in some parts, and 
a paste of soluble glass and asbestus in other 
parts are used as insulators. They are built 
up so as to form a cylinder within which 
the fire is maintained. The air is relied on 
to keep the outer junctions cool. The 
temperature does not exceed 200 C. (392 F.) 

Sixty such elements have an electro-motive force of 300 volts 
and an internal resistance of 1^ ohms. Such a battery requires 
the consumption of three cubic feet of gas per hour. (See Currents, 
Thermo-electric. ) 

Thermo=electric Call. A thermostat arranged to ring a bell or 
to give some indication when the temperature rises or falls beyond 




Fig. 332. Elements of 
Becquerel's Thermo- 
electric Batteries. 



532 



STANDARD ELECTRICAL DICTIONARY. 



certain points. It may be a compound bar of brass and steel fixed 
at one end and free for the rest of its length. Its end comes between 
two adjustable contacts. As the temperature rises it bends one way 
(away from the brass side) and, if hot enough, touching a contact 
gives one signal. If the temperature falls it curves the other way, 
and if cold enough touches the other contact, giving another signal. 
(See Thermostat, Electric.) 

Thermo=electric Couple. If two dissimilar conductors form 
adjacent parts of a closed circuit, and their junction is at a different 
temperature than that of the rest of the circuit, a current will result. 
Such pair of conductors are called a thermo-electric couple. They 
may be joined in series so as to produce considerable electro-motive 
force. (See Thermo-electricity and other titles in thermo-elec- 
tricity.) 

The efficiency of a thermo-electric couple according to the second 
law of thermo-dynamics is necessarily low — not over 10 per cent. 

Thermo=electric Diagram. A diagram indicating the change 
in potential difference for a fixed difference of temperature between 
different metals at different temperatures. It is laid out with 
rectangular co-ordinates. On one axis temperatures are laid off, 
generally on the axis of abscissas. On the other axis potential 
differences are marked. Different lines are then drawn, one for 
each metal, which show the potential difference, say for one degree 
centigrade difference of temperature between their junctions, pro- 
duced at the different temperatures marked on the axis of abscissas. 



%i?t «ooV <60"c jho'c ~_ n&t too*, «o*r «oo"c «*•** 





























Lead 






A 


.^ 






_e 


__CO£>p< 


















»<v>- 








e 










A 












^^ 



















Fig. 333. 



Thermo-electric Diagram, Giving Potential Difference in 
C. G. S. Units. 



Thus taking copper and iron we find at the temperature o c C. 
(32 F.) a difference of one degree C. (i.8° F.) in their junctions 
will produce a potential difference of 15.98 micro volts, while at 
274.5 C. (526. i° F.) the lines cross, and zero difference of potential 



STANDARD ELECTRICAL DICTIONARY. 533 

is indicated. Taking the lead line on the same diagram it crosses 
the iron line a little above 350 C. (662 F.), indicating that if one 
junction is heated slightly above and the other is heated slightly 
below this temperature no potential difference will be produced. 
Lead and copper lines, on the other hand, diverge more and more 
as the temperature rises. 

Thermo=eIectric Inversion. The thermo-electric relations of 
two conductors vary at different temperatures. Sometimes at a defi- 
nite point they have no electro-motive force and after passing this 
point the positive plate becomes a negative one and vice versa. 
This is inversion, or reversal. (See Thermo-electric Diagram.) 

Synonym — Thermo-electric Reversal. 

Thermo=eIectricity. Electric energy, electro-motive force or 
electrification produced from heat energy by direct conversion. It 
is generally produced in a circuit composed of two electric con- 
ductors of unlike material, which circuit must possess at least two 
junctions of the unlike substances. By heating one of these to 
a higher temperature than that of the other, or by maintaining one 
junction at a different temperature from that of the other a poten- 
tial difference is created accompanied by an electric current. 

In many cases differential application of heat to an identical 
material will develop potential difference. This effect, the con- 
verse of the Thomson effect, is not used to produce currents, as in 
a closed circuit the potential differences due to differential heating 
would neutralize each other. 

Thermo=eIectric Junction. A junction between two dissimilar 
conductors, which when heated or cooled so as to establish a 
differential temperature, as referred to the temperature of the other 
junction, produces potential difference and an electric current. 

Thermo=electric Pile, Differential. A thermo-electric pile 
arranged to have opposite faces subj ec ted to different sources of 
heat to determine the identity or difference of temperature of the 
two sources of heat. It corresponds in use to a differential air ther- 
mometer. 

Thermo=eIectric Power. The coefficient which, multiplying 
the difference of temperature of the ends of a thermo-electric 
couple, gives the potential difference, expressed in micro-volts. It 
has always to be assigned to a mean or average temperature of the 
junctions, because the potential difference due to a fixed difference 
of temperature between two metals varies with the average tem- 
perature of the two junctions. (See Thermo-electric Diagram.) 

For bismuth and antimony at 19^2 ° C. (67. i° F.) it is 103 micro- 
volts per degree Centigrade (i.8° F.). This means that if one June- 



534 



STANDARD ELECTRICAL DICTIONARY. 



tion is heated to 19 C. and the other to 20 C. (66. 2 F. and 68.0 
F.) a potential difference of 103 micro- volts will be produced. 

The potential difference is approximately proportional to the 
difference of temperature of the two junctions if such difference is 
small. Hence for large differences of potential the thermo-electric 
power coefficient does not apply. 

As a differential function it is thus deduced by Sir William 
Thomson, for expressing the E.M.F. in a thermo-electric circuit : 
If a circuit is formed of two metals with the junctions at indefin- 
itely near temperatures, t and t + dt, and dE is the E. M. F. of the 
circuit, then the differential coefficient dEjdt is called the thermo- 
electric power of the two metals for the temperature t. 

Thermo=eIectric Series. The arrangement of possible thermo- 
electric elements, q. v., in a table in the order of their relative 
polarity. Bismuth and antimony form a couple in which when 
their junction is heated the bismuth acts as the positive or nega- 
tively charged element and antimony as the negative or positively 
charged. Between these two extremes according to Seebeck the 
series runs as follows : 



Antimony, 


Silver, 


Copper, 


Arsenic, 


Gold, 


Platinum, 


Iron, 


Molybdenum, 


Palladium 


Steely 


Tin, 


Cobalt, 


Cadmium, 


Lead, 


Nickel, 


Tungsten , 


Mercury, 


Bismuth. 


Zinc, 


Manganese, 





A differential temperature of i°C. (i.8° F.) in a bismuth-anti- 
mony couple maintains a potential difference of 103 micro-volts. 

Matthiessen gives a different series ; it is arranged in two 
columns ; the first column has positive coefficients annexed the 
second has negative. On subtracting the greater one from the 
lesser, which, if the two elements are in different columns, of 
course amounts to adding after changing the negative sign, the 
relative potential difference due to the combination is obtained. 



Bismuth 


• 25 


Gas Coke 


O.I 


Cobalt 


9 


Zinc 


0.2 


Potassium . 


• 5-5 


Cadmium 


o-3 


Nickel 


5 


Strontium . 


2.0 


Sodium 


• 3- 


Arsenic 


3-8 


Lead 


1.03 


Iron 


5-2 


Tin 


1 


Red Phosphorous 


9.6 


Copper 


1 


Antimony . 


9.8 


Silver 


1 


Tellurium 


179.9 


Platinum 


0.7 


Selenium . 


290 



STANDARD ELECTRICAL DICTIONARY. 535 

Thus the relative E. M. F. of a bismuth-nickel couple, as both 
are in the + column , would be 25 — 5 = 20 ; that of a cobalt-iron 
couple, one being in the + column the other in the — column, 
would be 9 -f- 5.2 = 14.2. Alloys are not always intermediate to 
their constituents, and small amounts of impurities affect the 
results largely. This may account for the discrepancies of different 
observers. Other compounds could be introduced into the series. 

Artificial silver sulphide has been used by Becquerel in a 
thermo-electric battery. 

Thermo=electric Thermometer. A species of differential ther- 
mometer. It consists of two thermo-electric junctions connected 
in opposition with a galvanometer in the circuit. Any inequality 
of temperature in the two ends or junctions produces a current 
shown by the galvanometer. It may be used to determine the 
temperature of a distant place, one of the junctions being located 
there and the other being under control of the operator. If the 
latter junction is heated until no current is produced its tempera- 
ture is evidently equal to that of the distant couple or junction. 
The heating may be done with hot water or mercury, or other 
melted metal. The temperature of the water, or other substance, 
gives the temperature of the distant place. 

Thermolysis. Decomposition by heat ; dissociation. All com- 
pound bodies are decomposable by heat if it is intense enough. 
Hence at very elevated temperatures there can be no combustion. 

Synonym — Dissociation. 

Thermometer. An instrument for indicating the intensity of 
heat. Three scales of degrees of heat are used in practise, the 
Fahrenheit, R£amur, and Centigrade, each of which is described 
under its own title. (See Zero, Thermometric — Zero, Absolute.) 
The ordinary thermometer depends on the expansion of mercury ; 
in some cases alcohol is used. Besides these the compound bar 
principle as used in the thermostat (see Thermostat, Electric) is 
employed. 

Thermometer, Electric, (a) A thermometer whose indications 
are due to the change of resistance in conductors with change of 
temperature. Two exactly similar resistance coils may be electric- 
ally balanced against each other. On exposing one to a source of 
heat, its resistance will change and it will disturb the balance. The 
balance is restored by heating the other coil in a vessel of water 
when the temperature of the water gives the temperature of both 
coils. The coils are enclosed in water-tight metallic cases. 

Synonytn — Electric Resistance Thermometer. 

(5) A differential thermometer may be made by connecting with 
a pair of conductors, two thermo-electric couples in opposition to 



536 



STANDARD ELECTRICAL DICTIONARY. 



each other, and including a galvanometer in series. On heating the 
junction of one couple more than that of the other a current at once 
goes through the galvanometer. 

(c) (See Thermometer, Kinners ley's.) 

Synonym — Thermo-electrometer. 

Thermometer, Kinnersley's. A thermo-electrometer. A large 
glass tube is mounted on a standard and communicates with a small 
tube parallel to it. Water is poured in so as to rise in the small tube. 
Two wires terminating in bulbs enter the large tube by its top and 




Fig. 334. Kinnersley's Thermometer. 
bottom. The upper wire can be adjusted by moving up and down 
through a stuffing box. On discharging a Leyden jar through the 
space between the knobs on the two wires the water for a moment 
rises in the small tube. There is little or no accuracy in the instru- 
ment. It is allied to the electric mortar (see Mortar, Electric) as 
a demonstrative apparatus. 

Synonyms — Electric Thermometer — Thermo-electrometer. 

Thermo=multiplier. A thermo-electric battery including a num- 
ber of couples. The term is generally applied to a small battery 
with its similar junctions facing in one direction and used for re- 



STANDARD ELECTRICAL DICTIONARY. 



537 



peating Melloni's experiments on radiant energy, or so-called 
radiant heat. 

Thermophone. An apparatus for reproducing sounds telephonic- 
ally by the agency of heat ; a receiving telephone actuated by 
heat. ~ Thus a wire" may be attached to the centre of a diaphragm 
and kept in tension therefrom, and the transmitting telephone cur- 
rent may be caused to pass through it. The wire changes in 
temperature and consequently in length with the pulses of current 
going through it and vibrates the diaphragm, reproducing the 
sound. It is to be distinguished from the thermo-electric tele- 
phone which involves the action of potential difference produced 
by thermo-electric action. 

Thermostat, Electric. A thermostat or apparatus, similar to a 
thermometer in some cases, for closing an 
electric circuit when heated. It is used 
in connection with automatic fire alarms 
to give warning of fire. For this use a 
temperature of 52 C. (125 F.) is an 
approved one for setting one at, to com- 
plete the circuit. It is also applied to 
regulation of temperature, as in incu- 
bators. 

(a) One kind of thermostat consists of a 
compound bar wound into a spiral and 
fastened at one end, to which a terminal 
of a circuit is connected. The bar may 
be made of two strips of brass and iron 
riveted together, and wound into a spiral. 
When such a bar is submitted to changes 
of temperature it bends in different direc- 
tions, because brass expands and contracts 
more under changes of temperature than 
does iron. A contact point, to which the 
other terminal is connected, is arranged to 

make contact with the spiral at any desired degree of temperature, 
thus closing an electric circuit and ringing a bell, opening or 
closing a damper, or doing anything else to notify an attendant or 
to directly change the temperature. 

If the brass forms the outside of the spiral, increase of temperature 
makes the bending of the spiral bring the coils still closer. If the 
brass forms the inside, increase of temperature makes the spiral 
tend to become less close. As shown in the cut, the brass should 
lie along the inside of the spiral. 

Sometimes a straight compound bar is used, one of whose ends is 
fastened and the other is free. As the temperature changes such a 




Fig- 335- 
Electric Thermostat. 



538 STANDARD ELECTRICAL DICTIONARY. 

bar curves more or less, its free end moving to and fro. Two con- 
tact screws are provided, one on each side of its free end. If the 
temperature falls it makes contact with one of these ; if the tem- 
perature rises, it makes contact with the other. Thus it may close 
one of two circuits, one for a fall and the other for a rise in tem- 
perature. 

It is well to introduce a third bar between the brass and iron ones, 
made of some material of intermediate coefficient of expansion. 

(o) Another kind of thermostat comprises a vessel of air or other 
gas, which, expanding by heat, actuates a piston or other device 
and closes an electric circuit. 

Synonym — Electro-pneumatic Thermostat. 

(c) Another form utilizes the expansion of mercury. The mercury 
is made part of an open electric circuit. As it expands it conies in 
contact with the other terminal of the circuit, thus completing it, 
when the currenr gives an alarm or does as is provided for in the 
apparatus employed. 

Thermostats may be worked on either open or closed circuits ; 
normally the circuit may be open as described and may close on 
rise of temperature, or it may be normally closed and open as the 
temperature rises. 

Thomson Effect. In an unequally heated conductor the dif- 
ferential heating is either increased as in iron, or diminished as in 
copper by a current. In lead the phenomenon does not occur. It 
is termed the Thomson effect. It is intimately related to the 
Peltier effect. 

In a thermo-electric couple a heated junction is the source of 
electro-motive force, if heated more than other parts of the circuit. 
The current in a copper-iron junction flows from the copper to 
the iron across the heated junction. A hot section of an iron con- 
ductor next to a cold section of the same is a source of thermo- 
electricity, in the sense that the hot section is negative to the 
colder. A current passing from the hot to the cold iron travels 
against rising potentials, and cools the iron in the cooler parts. As 
it passes to the hotter parts it travels against falling potentials and 
hence heats the iron in these parts. In this way a current intensifies 
differential heating in an iron conductor. 

In copper the reverse obtains. In it the thermo-electric relations 
of hot and cold copper are the reverse of those of iron, and a cur- 
rent tends to bring all parts of a differentially heated copper con- 
ductor to an identical temperature. 

As a current travels in iron from hot to cold it absorbs heat ; in 
copper traveling from cold to hot it absorbs heat. 

The convection of heat by a current of electricity in unequally 



STANDARD ELECTRICAL DICTIONARY. 



539 



heated iron is negative, for it is opposed to that convection of heat 
which would be brought about by the flow of water through an 
unequally heated tube. In copper, on the other hand, the electric 
convection of heat is positive. (Daniell.) 

The above effects of the electric current upon an unequally 
heated conductor are termed the Thomson effects. In iron, at low 
red heat, they are reversed and are probably again reversed at 
higher temperatures. 

Three Wire System. A system of distribution of electric 
current for multiple arc or constant potential service. It is the 
invention of Thomas A. Edison. 

It includes three main wires which start from the central station 
or generating plant, and ramify with corresponding reduction in 
size, everywhere through the district or building to be lighted. 
As ordinarily carried out when dynamos are used, the dynamos 
are arranged in groups of two. One lateral lead starts from the 
negative binding post of one dynamo. The positive terminal of 
this dynamo connects to the negative of the other. Between the 
two dynamos the central or neutral lead is connected. The other 
lateral lead starts from the positive binding post of the second 
dynamo. 

The lamps or other appliances are calculated for the potential 
difference of a single dynamo. They are arranged between the 
neutral wire and the laterals, giving as even a disposition as 
possible to the two laterals. 

If evenly arranged and all burning or using current, no current 



m 



ill 




Fig". 336. Diagram of Three Wire System Showing Neutral Wire. 

goes through the neutral wire. If all the lamps situated on one 
lateral are on open circuit all the current goes through the neutral 
wire. In other cases the neutral wire receives the excess of 
current only. 

The advantages of the system are that it uses smaller wire than 
the two wire system for lamps of the same voltage. If lamps of 
double the voltage were used the two wire system would be most 
economical. 

Four wire and five wire systems have been more or less used, 
based on identical considerations, and involving in each case the 



54o STANDARD ELECTRICAL DICTIONARY. 

coupling of three or of four dynamos respectively, or else employ- 
ing a dynamo with special armature connections to give the 
requisite three-fold or four-fold division of total potential. In the 
five wire system the total voltage is four times that of a single 
lamp, the lamps are arranged four in series across the leads and 
the central wire is the only one that can be considered a neutral 
wire. When lamps are burning entirely from three side-leads they 
constitute a sort of three wire system by themselves, and their 
central wire may for the time be a neutral wire. 

In some of the three wire mains, especially in the larger sizes, 
the neutral wire is made of much smaller section than that of 
a lateral conductor, because in extensive districts it is practically 
impossible that the current should be concentrated in the neutral 
wire. 

Throw. In a galvanometer the instantaneous deflection of the 
needle when the contact or closing of the circuit is instantaneous, 
or when the discharge is completed before the needle begins to 
move. The throw of the needle is the datum sought when the 
ballistic galvanometer is used. 

Synonym — Elongation . 

Throw=back Indicator. A drop annunciator, whose shutter or 
drop is electrically replaced. 

Thrust=bearings. Bearings to support the end-thrust or push 
of a shaft. In disc armatures where the field-magnets attract the 
armatures in the direction of their axis of rotation, thrust-bearings 
have to be provided. In ordinary cylinder or drum armatures end- 
thrust is not applied, as a little end motion to and fro is considered 
advantageous as causing more even wear of the commutator surface. 

Thunder. The violent report which, as we hear it, succeeds the 
lightning flash in stormy weather. It is really produced simulta- 
neously with the lightning and is supposed to arise from disturbance 
of the air by the discharge. The rolling noise has been attributed 
to successive reflections between clouds and earth, and to series 
of discharges reaching the ear from different distances and through 
air of varying density. The subject is obscure. By timing the 
interval from lightning flash to the report of the thunder an approx- 
imate estimate of the distance of the seat of discharge can be made. 
The first sound of the thunder should be timed. An almost concur- 
rence of thunder and lightning indicates immediate proximity of 
the discharge. 

Ticker. A colloquial name for a stock or market report automatic 
printing telegraph, which prints its quotations and messages on a 
long tape. 



STANDARD ELECTRICAL DICTIONARY. 541 

Time Constant, (a) When current is first turned into a circuit 
of considerable self-induction it is resisted rather by the inductance 
than by the resistance. It is governed by the ratio of resistance 
and self-induction and this factor represents the time which it takes 
for the current to reach a definite fraction of its final strength. This 
fraction is -i.irti ior °-^3- 2 -7 1 ^3 * s the base of the Napierian 
system of logarithms. Thus if in any circuit we divide the in- 
ductance in henries by the resistance in ohms, the ratio gives the 
time-constant of the circuit, or it expresses the time which it will 
take for the current to reach 0.63 of its final value. 

(b) In a static condenser the time required for the charge to fall 
to 1/2. 7183th part of its original value. 

Time Cut=outs. Cut-outs which automatically cut storage bat- 
teries out of the charging circuit when they are sufficiently charged. 

Time=fall. In a secondary battery the decrease with use of electro- 
motive force maintained by a primary or secondary battery. As 
the battery becomes spent its voltage falls. The conditions of the 
fall are represented by its discharging curve. (See Curve, Dis- 
charging.) 

Time=reaction. A term in electro-therapeutics ; the period of 
time occupied in the passage of the effects of an electric current 
from nerve to muscle. 

Time=rise. In a secondary battery the increase of electro- 
motive force produced during the charging process. Its rate and 
conditions are graphically shown in the charging curve. (See 
Curve, Charging.) 

Tin. A metal ; one of the elements ; symbol, Sn ; atomic 
weight, 117. 8 ; equivalent, 58.9 and 29.5 ; valency, 2 and 4 ; specific 
gravity, 7.3. It is a conductor of electricity. 

Relative resistance, compressed, (Silver == 1) 8.784 

Specific resistance at o° C. (32 F.), 13.21 microhms. 
Resistance of a wire at o° C. (32 F.), 

(a) 1 foot long, weighing 1 grain, 1-380 ohms. 

(6) 1 foot long, 1 -1000 inch thick, 79-47 " 

(c) 1 meter long, weighing 1 gram, -9632 " 

(d) 1 meter long, 1 millimeter thick, .1682 " 
Resistance of a 1 inch cube at o° C. (32 F.), 5.202 microhms. 
Percentage of variation in resistance per degree C. (i.8° F.), at 

about 20 C. (68° F.), .365 per cent. 

Electro-chemical equivalent (hydrogen = .0105), .619 mgs. 

.310 " 



542 



STANDARD ELECTRICAL DICTIONARY. 



Tinnitus, Telephone. A nervous affection of the ear, of the 
order of professional cramp ; it is attributed to too much use of the 
telephone. 

Tin Sounders. A recent addition to the single needle telegraph. 
(See Telegraph, Single Needle.) It 
consists of small tin plates, cut and 
bent, and so fitted in pairs to the in- 
strument, that the needle as deflected 
strikes one or the other on its right 
and left hand movements. The sound- 
ers can be made to give sufficiently 
distinctive sounds to make sound-read- 
ing, q. v., possible. Commercial tin 
plate, which is really tinned iron, seems 
to give the best results. 

A solution 
It is corn- 




Fig. 337. Tin Sounders. 



Tissandier's Solution. 

for bichromate batteries. 
posed as follows : 
Water, 100 parts by weight — potassium bichromate, 16 parts — 
66° sulphuric acid, 37 parts. 

Tongue of Polarized Relay. The German silver extension of 
the vibrating or oscillating member of a polarized relay, corre- 
sponding to the armature of an ordinary relay. 

Tongue of Polarized Relay, Bias of. In a Siemens' polarized 
relay the pole pieces are adjustable so that they may be brought 
nearer to or withdrawn from the tongue. One of the poles is ad- 
justed so as to be nearer the tongue. This one-sided adjustment is 
the bias. Its effect is that when the relay is unexcited this pole 
attracts the armature so that it normally is drawn towards it. This 
ensures the normal contact of the tongue either with the contact 
point, or with the insulated stop piece or adjustment screw. With- 
out bias the armature remains in contact with or drawn towards 
whichever pole it was last attracted to. In its usual use a bias is 
given it. 

Top, Magnetic. A toy illustrating magnetic attraction. It 
consists of a disc or body of lead or other material, through 
which a magnetized steel spindle pointed at its lower end is thrust. 
A number of short pieces of iron wire are used with it. It is spun 
like an ordinary top upon the point of the spindle and one of the 
pieces of iron wire is laid by the side of its point. As it turns the 
magnetic adherence causes the piece of wire to be carried along 
in one direction by the rotation of the spindle, until the end is 
reached, when it goes over to the other side of the spindle and 
travels back again. 



STANDARD ELECTRICAL DICTIONARY. 543 

By using bent pieces of wire of various shapes the most curious 
effects are produced. Circles and S shaped pieces give good effects. 




Fig. 338. Magnetic Top. 

To increase the mysterious effect covered iron wire (bonnet wire) 
may be employed. 

Torpedo, Electric. (a) A fish, the Rata Torpedo, which 
possesses the power of giving electric shocks. (See Ray, Electric.) 

(b) An instrument of war ; a torpedo whose operations include 
electrical discharge or other electric function or factor of operation. 

Torpedo, Sims=Edison. A torpedo driven by an electric motor, 
and also steered by electricity. Its motions are all controlled from 
the shore. The torpedo proper is carried some distance below the 
surface of the water by a vessel immediately above it, from which 
it is suspended by two rigid bars. In the torpedo is a cable reel 
on which the conducting cable is disposed. An electric motor and 
controlling gear are also contained within the torpedo. In its 
front the explosive is placed. It is driven by a screw propeller 
actuated by the electric motor. As it moves it pays out cable so 
that it has no cable to draw after it through the water, the cable 
lying stationary in the water behind it. This avoids frictional 
resistance to its motion. The maintenance of the torpedo at a 
proper depth is one of the advantages of the system. 

Torque. A force tending to produce torsion around an axis. 
An example is the pulling or turning moment of an armature of 
an electric motor upon its shaft. It is often expressed as pounds 
of pull excited at the end of a lever arm one foot long. 

The expression is due to Prof. James Thompson, then of the 
University of Glasgow. 

1 ' Just as the Newtonian definition of force is that which pro- 
duces or tends to produce motion (along a line), so torque may 



544 STANDARD ELECTRICAL DICTIONARY. 

be defined as that which produces or tends to produce torsion 
(around an axis) . It is better to use a term which treats this action 
as a single definite entity than to use terms like ' couple' and 
' moment,' which suggest more complex ideas." (S. P. Thomp- 
son.) 

A force, acting with radius r gives a torque equal to f X r ; y*and 
r may be expressed in any units. S. P. Thompson gives the fol- 
lowing equivalents : 
To reduce 

dyne-centimeters to gram centimeters, divide by 981 
dyne-centimeters to meter-kilograms divide by 981 X io 5 
dyne-centimeter, to pound-feet divide by J3-56 X io b 

pound- feet to meter-kilograms divide by 7.23 

In each of these compound units the first unit is the force and 
the second unit is the radius or lever arm of the torque. 

Synonyms — Turning Moment — Moment of Couple — Axial Coupie 
— Angular Force — Axial Force. 

Torsion Balance, Coulomb's. Originally an apparatus in which 
electrostatic attraction or repulsion is measured against the torsion 
of a filament, often of silk-worm cocoon fibre. It consists in 
one form of a cylindrical glass vessel in which a light shellac 
needle is suspended horizontally by a fibre. This needle carries at 
one end a gilded disc or sphere and is suspended by a fine wire, or 
filament. A proof plane, q. v., is excited by touching it to the 
bcdy under trial ; it is then inserted in the case. The disc on the 
needle is first attracted and then repelled. The position finally 
taken by the needle is noted. The force of torsion thus produced 
is determined by. twisting the filament by the torsion head on the 
top of the apparatus so as to move the needle a certain distance 
towards the proof plane. The more the torsion-head has to be 
turned to carry the needle through a specified arc the greater is the 
torsion effected or the greater is the repulsion exerted, The tor- 
sional force of a wire is proportional to the angle of torsion ; this 
gives the basis for the measurement. 

With magnetic needle it is used to measure magnetic repulsion 
and attraction. The best material for the filament is quartz, but the 
instrument is not very much used. 

Torsion Galvanometer. A galvanometer in which the torsion 
required to bring the index back to zero, when the current tends 
to displace it, is made the measure of the current strength or of 
the electro-motive force. It involves the use of a torsion head, q. v., 
or its equivalent. 

Torsion Head. The handle and disc from whose undersurface 



STANDARD ELECTRICAL DICTIONARY. 545 

the filament depends to which the needle or magnet is attached. It 
is turned to measure the torsional effect, the edge of the disc being 
marked or graduated so as to give the angle of deflection required 
to overcome the effect of the torque of the needle. 

Torsion Suspension. Suspension by one or more wires, fibres, 
or ribands, involving the restitutive force of torsion. Thus fibre 
suspension, q. v., is a variety of torsion suspension. 

Often a single riband of steel stretched horizontally and secured 
at both ends is used, the suspended object, e. g., a balance beam, 
being attached at its own centre to the centre of the stretched 
riband. Quite sensitive balances are constructed on this principle. 
It is peculiarly available where an electric current is to be transmit- 
ted, as absolute contact is secured, as in William Thomson's ampere 
balances. 

Touch. A term applied to methods of magnetization, as " single 
touch," " double touch, " or " separate touch," indicating how the 
poles of the inducing magnet or magnets are applied to the bar to be 
magnetized. Under the titles of Magnetization the different 
methods are described. 

Tourmaline. A mineral ; a subsilicate ; characterized by the 
presence of boric trioxide, which replaces aluminum oxide. It is 
notable for possessing pyro-electric properties. (See Pyro-elec- 
tricity. ) 

Tower, Electric. The tower used in the tower system, q. v., of 
arc light illumination. 

Tower System. In electric lighting the system of lighting 
extended areas by powerful arc lamps placed on high towers, gen- 
erally of iron or steel frame- work. The lights are thus maintained 
at a high elevation, giving greater uniformity of illumination than 
if they were lower, but at the expense of considerable light which is 
lost. Sometimes wooden masts are employed instead of towers. 

The principle involved is that the intensity of light at any place 
given by a source of illumination varies with the square of its 
distance from the place in question. Hence in using strong arc 
lights it is an object to have the distances of all parts of the area 
illuminated at as nearly uniform distances from the light as possible. 
An approximation to uniformity is secured by placing the lamps 
at a very high elevation. 

Transformer. In alternate current lighting the induction coil 
by which the primary current with high initial electro-motive force 
is caused to produce a secondary current with low initial electro- 
motive force. 



546 STANDARD ELECTRICAL DICTIONARY. 

A typical transformer consists of a core of thin iron sheets. The 
primary is of comparatively thin wire and often of ten or more 
times as many turns as the secondary. The latter is of thicker 
wire. Where the ratio of 10 to i as regards number of turns in the 
primary and secondary obtains, the initial E. M. F. of the second- 
ary is one-tenth that of the primary circuit. 

The cores are laminated, as described, to avoid the formation of 
Foucault currents. 

The counter-electro-motive force of the transformer when the 
secondary circuit is open, prevents any but the slightest current 
from passing through the primary. In proportion as the secondary 




Fig 339. Ferranti's Transformer. 

is closed and its resistance diminished, as by lighting more lamps 
in parallel, the counter-electro-motive force of the transformer falls 
and more current passes through the primary. 

The economy of the apparatus is in the fact that counter-electro- 
motive force reduces current through a conductor without absorb- 
ing any energy. A resistance coil cuts down a current, but absorbs 
energy equal to the current multiplied by the potential difference 
between the terminals of the coil. This electric energy is con- 
verted into heat energy and is wasted. But the counter-electro- 
motive force of a transformer is exerted to reduce current without 
production of heat and with little waste of energy. This is one of 



STANDARD ELECTRICAL DICTIONARY. 547 

the advantages of the alternating current system of distribution of 
electric energy. 

The object of a transformer being to secure safety to the person 
or to life by the separation of the high potential primary or street 
circuit, and the low potential house circuit, any contact of the two 
circuits in the converter is a source of danger. Special care should 
be taken to ensure absence of leakage, as it is termed. Mica or 
other insulation is sometimes employed to prevent the wires from 
coming in contact by piercing or sparking with the core and with 
each other. 

Transformer, Commuting. A type of continuous current 
transformer, resembling a dynamo with armature and field both 
stationary, but with revolving commutator, by which the magnetic 
polarity of a double wound armature is made to rotate. This 
secures the desired action, of a change or lowering of potential. 

Transformer, Continuous Alternating. An apparatus for 
transforming a continuous into an alternating current or the 
reverse. The combination of a continuous current dynamo with 
an alternating current one is sometimes employed. It is a form of 
motor dynamo. 

Another type is a regular dynamo with ordinary commutator 
and with, in addition thereto, two, three or four contact rings, con- 
necting to as many symmetrically disposed points in the winding 
of the armature. This will give out or receive alternating currents 
of two, three or four phases according to the number of collecting 
rings. One winding serves for both alternating and continuous 
currents. 

Transformer, Continuous Current. A machine of the dynamo 
type for changing the potential of a circuit. In one form two 
armatures are mounted on one shaft in a single field or in separate 
fields ; one is a motor armature driven by the original current ; 
the other generates the new current. This is a motor dynamo. In 
1874 Gramme constructed a machine with ring armature with two 
windings, of coarse and fine wire respectively, and with independent 
commutators. Such dynamo could transform currents up or down. 

Continuous current transformers have attained an efficiency of 
83 per cent, at full load, and of 75 per cent, at half load. Owing to 
the balancing of the self-inductions of the two windings these 
machines do not spark. As the driven and driving parts are con- 
tained in one rotating part their friction is very slight. 

Transformer, Core. A transformer wound upon an enclosed 
core, such as the hedgehog transformer (see Transformer, Hedge- 
hog), or common induction coil. 




548 STANDARD ELECTRICAL DICTIONARY. 

Transformer, Hedgehog. An induction coil transformer whose 
iron core is composed of a bundle of iron wires, which after the 
wire windings are in place have their ends 
spread out to reduce to some extent the 
reluctance of the circuit, which at the best 
is high, as the air acts as the return circuit. 
This transformer has a low degree of hys- 
teresis ; and its efficiency for very small 
loads or for no load is superior to that of the 
closed magnetic circuit transformer. 

Transformer, Multiple. A transformer 
connected in parallel with others between 
the two leads of the primary circuit. The 
term refers to the connection only and not 
to any peculiarity of the transformer itself. 

Transformer, Oil. A transformer with 
oil insulation. The advantage of this insu- 
lation is that if pierced it at once closes, so 
that no permanent injury ensues. It is a 
self-healing form of insulation. 

Transformer, Series. Transformers con- 
Fig: 340. nected in series upon the primary circuits. 

Swinburne s Hedgehog . r m r j 

Transformer. The term, like "multiple transformers, 

only applies to the connection, not to the 
transformer. Series transformers are but little used. 

Transformer, Shell. A transformer with its iron core entirely 
outside of and enclosing the primary and secondary winding. It 
may be made by the use of outer iron wire windings as core. 

Transformer, Welding. The transformer used for electric 
welding. (See Welding, Electric.) It is a transformer with very 
long primary and exceedingly short and thick secondary. It is used 
with the alternating current in the primary, and produces in the 
secondary circuit which includes the bars to be welded a very low 
potential difference. 

Owing to the very low resistance of the secondary circuit this 
low electro-motive force produces a very strong current, which 
develops the requisite heat. The same type of transformer is 
used for brazing and similar purposes. 

Transmitter. In general electric phraseology, any instrument 
which produces signals to be transmitted through a line or circuit 
is a transmitter. Thus the Morse key in telegraphy or the Blake 
transmitter in telephony are examples of such. 



STANDARD ELECTRICAL DICTIONARY. 549 

Transmitter, Carbon. A form of microphone used as a tele- 
phone transmitter. (See Carbon Telephone.) 

Transposing. A method of laying metallic circuits for telephon- 
ing. The wires at short intervals are crossed so that alternate 
sections lie on opposite sides of each other. It is done to avoid 
induction. 

Transverse Electro=motive Force. Electro-motive force in 
a substance in which electric displacement is taking place, produced 
by a magnetic field. It is sometimes assigned as the cause of the 
Hall effect, q. v. 

Trimmer, Brush. A shears for cutting off evenly and squarely 
the ends of copper dynamo brushes. The brushes when uneven 
from wear are removed from the brush holders, and their ends are 
sheared off in the trimmer. 

Trolley. A grooved metallic pulley or set of pulleys which runs 
along an active wire of a circuit, a lead from which trolley goes to 
earth or connects with another wire, so that the trolley takes cur- 
rent generally for operating a street car motor placed upon the 
circuit leading from it ; a rolling contact with an electric lead. 

Trolleys are principally used on electric railroads, and are now 
universally of the sub-wire system, being at the end of a pole which 
is inclined backward and forced upward by springs, so as to press 
the trolley against the bottom of the wire. Thus the trolley does 
not increase the sagging of the wire, but tends to push it up a little 
in its passage. 

Trolley, Double. A trolley with two rollers or grooved wheels, 
placed side by side, and running on two parallel leads of wire. It is 
adapted to systems employing through metallic trolley lines with 
the motors in multiple arc, connecting or across the two leads. 

Trolley Section. An unbroken or continuous section of trolley 
wire. 

Trouve's Solution. An acid exciting and depolarizing solution for 
a zinc-carbon battery. Its formula is as follows : Water, 80 parts ; 
pulverized potassium bichromate, 12 parts ; concentrated sulphuric 
acid, 36 parts ; all parts by weight. The pulverized potassium bi- 
chromate is added to the water, and the acid is added slowly wdth 
constant stirring. As much as 25 parts potassium bichromate may 
be added to 100 parts of water. The heating produced by the acid 
and water dissolves nearly all the potassium salt. Use cold. 

True Contact Force. A species of electro-motive force whose 
existence is supposed to be proved by the Peltier effect. The 
lowering in temperature of a contact of dissimilar metals is attrib- 
uted to a force that helps the current on its way if in the direction 



550 STANDARD ELECTRICAL DICTIONARY. 

of thermo-current proper to the junction and opposing it if in the 
reverse. The true contact force is taken to explain this phenom- 
enon ; thermo-electric force cannot, as there is no heat or cold 
applied to the junction. 

Trumpet, Electric. An apparatus consisting of a vibrating 
tongue, kept in motion by electricity as in the buzzer, q. v., placed 
in the small end of a trumpet-shaped tube. 

Trunking Switchboard. A telephone switchboard arranged in 
sections, which sections are connected by trunk lines, through 
which trunk lines the desired connections are made. 

Trunk Lines. In telephone distribution systems, the lines con- 
necting different stations, or different sections of a switch-board 
and used by any one requiring such connections ; one trunk line 
answers for a number of subscribers. 

Tube, Electric. A tube of glass around which is pasted a series 
of tinfoil circles, diamonds, or little squares, or other form of inter- 
rupted conductor. The' pieces generally are placed in the line of 
a spiral. When a static discharge of electricity takes place along 
the conductor a row of bright sparks is produced at the breaks in 
the conductor. These by reflection are multiplied apparently, and 
a beautiful effect of intersecting or crossing spirals of sparks is 
presented. 

The experiment is in line with the luminous pane and lightning 
jar, and is used merely as a demonstration, or lecture experiment. 

Synonym — Luminous Tube. 

Tubular Braid. A braid woven of tissue or worsted, and tubular 
or hollow. Its object is to provide a covering which can be drawn 
over joints in covered wires. In making the joint the ends of the 
wires are necessarily bared, and a short piece of tubular braid is used 
for covering them. It is drawn by hand over the joint. 

Turns. An expression applied to the convolutions of wire in a 
solenoid, electro-magnet, or other apparatus or construction of that 
kind. A turn indicates a complete encircling of the core or axis 
of the object. Thus a wire wound five times around a bar gives 
five turns. 

While this is its primary meaning the term if compounded may 
refer to virtual turns. Thus an ampere-turn means one ampere 
passing through one turn. But ten ampere-turns may mean ten 
amperes passing through ten turns, five amperes passing through 
two turns, and so on. This use is analogous to a dimension of 
length in a compound word, as foot-pound. 

There may be a number of kinds of turns qualified by descriptive 
adjectives, as series-turns, the turns of wire in a series circuit of a 



STANDARD ELECTRICAL DICTIONARY. 551 

compound dynamo. In the same way there are shunt-turns. If 
series ampere-turns or shunt ampere-turns are meant the word 
ampere should be included. 

Turns, Dead, of a Dynamo. The rotations of a dynamo arma- 
ture while it is building itself up or exciting itself. The expression 
is a bad one, as it is likely to be confounded with the dead turns 
of armature wire. 

Turns, Primary Ampere=. The ampere-turns in a primary cir- 
cuit of an induction coil or transformer. In an electric welding 
transformer, or in the transformer used in the alternating current 
system, where efficiency is an important element, the ampere-turns 
in primary and secondary for an efficiency of 100 per cent, should 
be equal. In the case of an experimental induction coil other 
considerations outweigh that of mere efficiency. Insulation, in- 
cluding security from piercing, and the production of as long a 
spark as possible, are, in these cases, the controlling consideration. 

Turns, Secondary Ampere=. The ampere-turns on the second- 
ary circuit of an induction coil or transformer. These depend on 
the path provided for the current. If of negligible inductance, such 
as a number of incandescent lamps would provide, the ampere-turns 
should be equal to those of the primary coil. (See Turns ', Primary 
Ampere-.) 

Typewriter, Electric. A typewriter in which the work of 
printing or of pressing the type faces against the paper, or printing 
ribbon, is done by electro-magnetic attraction. The keys close 
electric circuits, throwing the electro-magnetic action into play. 
This involves the use of electricity for what is ordinarily only a 
mechanical process. The strength of the impression, however, is 
independent of the touch of the operator. It has not come into 
very extensive use. 

Ultra=gaseous Matter. Gas so rarefied that its molecules do 
not collide or very rarely do so. 

Experiments of very striking nature have been devised by 
Crookes and others to illustrate the peculiar phenomena that this 
matter presents. The general lines of this work are similar to the 
methods used in Geissler tube experiments, except that the vacua 
used are very much higher. 

When the vacuum is increased so that but one-millionth of the 
original gas is left the radiant state is reached. The molecules in 
their kinetic movements beat back and forth in straight lines with- 
out colliding, or with very rare collisions. Their motions can be 
guided and rendered visible by electrification. A tube or small 
glass bulb with platinum electrodes sealed in it, is exhausted to the 
requisite degree and is hermetically sealed by melting the glass. 



552 STANDARD ELECTRICAL DICTIONARY. 

The electrodes are connected to the terminals of an induction coil 
or other source of high tension electrification. The molecules 
which come in contact with a negatively electrified pole are 
repelled from it in directions normal to its surface. They produce 
different phosphorescent or luminous effects in their mutual col- 
lisions. 

Thus if they are made to impinge upon glass, diamond or ruby, 
intense phosphorescence is produced. A piece of platinum sub- 
jected to molecular bombardment is brought to white heat. A 
movable body can be made to move under their effects. Two 
streams proceeding from one negative pole repel each other. The 
stream of molecules can be drawn out of their course by a mag- 
net. 

The experiments are all done on a small scale in tubes and bulbs, 
resembling to a certain extent Geissler tubes. 

Unbuilding. The loss of its charge or excitation by a self-exciting 
dynamo. It is the reverse of building-up. The latter indicates 
the exciting of the field by the action of the machine itself; the 
former the spontaneous loss of charge on open circuit or from other 
cause. 

Underground Conductor. An electric conductor insulated and 
placed under the surface of the earth, as distinguished from aerial 
conductors. 

Underground Electric Subway. A subway for the enclosing 
of electric telegraph and other conductors under the surface, gener- 
ally in the line of streets, to do away with telegraph poles and 
aerial lines of wire. Many systems have been devised. The gen- 
eral type includes tubes called ducts in sets, called conduits, 
bedded in concrete or otherwise protected. Every two or three 
hundred feet the sets lead into a cistern-like cavity called a man- 
hole. The insulated wires or cables, generally sheathed with a 
lead alloy, are introduced into the tubes through the man-holes. A 
rope is first fed through the tube. To do this short rods which 
screw together are generally employed. One by one they are 
introduced, and each end one is screwed to the series of rods 
already in the duct. When the end of the duct is reached the rope 
is fastened to the last rod, and the rods are then drawn through, 
unscrewed one by one and removed, the rope following them. By 
means of the rope a windlass or capstan may be applied to draw 
the cable into the duct. At least at every second man-hole the 
cables have to be spliced. 

Each cable may contain a large number of conductors of small 
size for telephoning, or a smaller number for electric light and 
power. The tendency is now to separate the different classes of 
wires in important lines, placing the heavier wires on one side of 



STANDARD ELECTRICAL DICTIONARY. 553 

the street and the telephone and telegraph wires on the other. 
This of course necessitates two separate conduits. 

The advantage of underground distribution affects not only the 
appearance of streets in doing away with unsightly telegraph poles, 
but it also removes an element of danger at fires. Aerial wires 
interfere greatly with the handling of ladders at fires, and expose 
the firemen who attempt to cut them to danger to their lives from 
shock. 

Unidirectional, adj. Having one direction asa n unidirectional 
current" or " unidirectional leak." The term is descriptive, and 
applicable to many cases. 

Uniform, adj. Unvarying ; as a uniform potential difference, uni- 
form current or conductor of uniform resistance per unit of length. 
The term is descriptive, and its application and meaning are 
obvious. 

Uniform Field of Force. A field of evenly distributed force ; 
one in which the number of lines of force per unit of area of any 
equipotential surface is the same. 

Unipolar, adj. Strictly speaking this term means having only 
one pole, and is applied to magnets, armatures and the like. In 
its use a solecism is involved, for there is no such condition possible 
as unipolar magnetism or distribution of magnetism. An example 
of its use is shown in unipolar magnets. (See Magnet, Unipolar.) 

Unipolar Armature. An armature of a unipolar dynamo ; an 
armature whose windings continuously cut the lines of force about 
the one pole, and hence whose polarity is unchanged in its rotation. 

Unipolar Current Induction. Current induction produced by 
moving a conductor through a magnetic field of force so that it 
always cuts the lines in similar relation to itself. Thus it produces 
a constant current through its own circuit, if a closed one, and no 
commutator is required. As this case always in practice amounts 
to the cutting of lines of force in the neighborhood of a single pole 
the term unipolar is employed to designate the action. 

The simplest representation of unipolar induction is the rotating 
of a conductor around the end of a bar magnet, its axis of rotation 
corresponding with the axis of the magnet. 

Unipolar Dynamo. A dynamo in which one part of the con- 
ductor slides on or around the magnet, so as always to cut lines of 
force near the same pole of the magnet. 

Unit. A directly or indirectly conventional and arbitrary quan- 
tity, in terms of which measurements of things with dimensions 
expressible in the chosen units are executed. 



554 STANDARD ELECTRICAL DICTIONARY. 

Thus for length the c. g. s. unit is the centimeter ; the B. E. unit 
is the foot. 

Unit, Absolute. A unit based on the three fundamental units 
of length, mass and time. These units are the centimeter, gram 
and second. Each one in itself may be termed a fundamental 
absolute unit. The system of such units is termed the centimeter- 
gram-second system. 

Unit, Angle. A factor or datum in angular velocity, q. v. It 
is the angle subtended by a portion of the circumference equal in 
length to the radius of the circle. It is equal very nearly to 57 
.29578° or 57 if 44.8". 

Unit, B. A. This term, while logically applicable to any of the 
British Association units, is often restricted to the ohm as formerly 
denned by the British Association, the B. A. Unit of Resistance, q. v. 

Unit, Fundamental. The three units of length, mass and time, 
the centimeter, gram and second, are termed fundamental units. On 
them is based the absolute system of units, and on multiples of 
them the practical system of units. 

Unit Jar. A Leyden jar which is used as a unit of measure of 
charge. 

It consists of a Leyden jar about 4 inches long and % inch 
diameter, with about 6 square inches of its outer and the same of 
its inner surface coated with tinfoil. It is placed between a source 
of electricity and a larger jar or battery of jars which is to be charged. 
The inner coating connects with the machine ; the outer coating 
with the jars to be charged. Short conductors terminating in 
knobs connect with inner and outer coatings, and the knobs are 
adjusted at any desired distance apart. 

By the charging operation the large jar or battery of jars receives 
a charge by induction, and the charge of the small jar is at first 
equal to this quantity. After a while a spark passes from knob to 
knob, discharging the small jar. This indicates the reception by the 
large jars of the quantity of electricity represented by the charge 
of the small jar. The charging goes on, and for every spark 
approximately the same quantity of electricity is received by the 
larger jars. 

The sparking distance m is directly proportional to the quantity 
of electricity, and inversely proportional to the area of coated sur- 
face, or is proportional to the potential difference of the two coats. 
This is only true for short sparking distance, hence for accuracy 
the knobs should be adjusted not too far from each other. 

Unit of Supply. A commercial unit for the sale of electric 
energy, as defined provisionally by the English Board of Trade ; 



STANDARD ELECTRICAL DICTIONARY. 555 

1,000 amperes flowing for one hour under an E. M. F. of 1 volt; 
3,600,000 volt- coulombs, or 1,000 watt-hours, are its equivalent. It 
is equal to %° B ° = 1.34 electric horse power. 
Synonym — Board of Trade Unit. 

Units, Circular. A system of units of cross-sectional area, 
designed especially for use in describing wire conductors. The 
cross-sectional area of such is universally a circle, and the areas of 
two wires of different sizes vary with the square of their radii or 
diameters. Hence if the area of a circle of known diameter is deter- 
mined it may be used as a unit for the dimensions of other circles. 
Any other circle will have an area proportioned to the area of the 
unit circle, as the squares of the diameters are to each other. 

In practise the commonest circular unit is the circular mil. This 
is the area of a circle one mil, T qVo inch, in diameter and is equal 
to .0000007854 square inch. A wire two mils in diameter has an 
area of four circular mils ; one ten mils in diameter has an area of 
one hundred circular mils. 

Thus if the resistance of a given length of wire 1 mil in diameter 
is stated, the corresponding resistance of the same length of wire of 
the same material, but of other diameter, is given by dividing 
the first wire's resistance by the square of the diameter in mils of 
the wire in question. 

As it is a basic unit, most conveniently applied by multiplication, 
the smaller units are used ; these are the circular mil, and circular 
millimeter. 

Units, Derived. Units derived by compounding or other pro- 
cesses, from the three fundamental units. Such are the units of area, 
volume, energy and work, momentum and electric units generally. 
In some cases the dimensions of the derived unit may reduce to those 
of a simple unit as inductance reduces to length, but the unit, as 
deduced from the fundamental ones, is still a derived unit. 

Units, Practical. A system of units employed in practical 
computation. The absolute units, especially in electricity, have 
been found too large or too small, and the attempt to make them 
more convenient has resulted in this system. It is based on exactly 
the same considerations as the absolute system of units, except 
that multiples of the original fundamental units of length, mass, 
and time have been taken as the base of the new system. These 
basic units are multiples of the fundamental units. They are the 
following : The unit of length is io 9 centimeters ; the unit of mass 
is io- 11 gram ; the unit of time remains 1 second. 

While this has conduced to convenience in giving better sized 
units, micro- and mega-units and other multiples or fractions have 



556 STANDARD ELECTRICAL DICTIONARY. 



to be used. The following are the principal practical electric 
units : 


Electrostatic C. G. 
Units. 
Intensity — Ampere equal to 3 X io 9 
Quantity — Coulomb " 3 X io 9 
Potential— Volt " | X io- 2 
Resistance — Ohm " J X io- 11 
Capacity — Farad " 9 X io 11 


S. 


Electromagnetic 
C. G. S. Units. 
io- 1 
io- 1 

IO 8 
IO 9 
IO- 9 



Universal Battery System. A term in telegraphy. If several 
equal and high resistance telegraphic circuits are connected in 
parallel with each other from terminal to terminal of a battery of 
comparatively low resistance each circuit will receive the same 
current, and of practically the same strength as if only one circuit 
was connected. This is termed the universal battery system. It 
is a practical corollary of Ohm's law. The battery being of very 
low resistance compared to the lines the joining of several lines 
in parallel practically diminishes the total resistance of the circuit 
in proportion to their own number. Thus suppose a battery often 
ohms resistance and ten volts E. M. F. is working a single line of 
one hundred ohms resistance. The total resistance of the circuit 
is then one hundred and ten ohms. The total current of the cir- 
cuit, all of which is received by the one line is 10 -f- no = .09 
ampere, or 90 milliamperes. Now suppose that a second line of 
identical resistance is connected to the battery in parallel with the 
first. This reduces the external resistance to fifty ohms, giving a 
total resistance of the circuit of sixty ohms. The total current of 
the circuit, all of which is received by the two lines in equal parts, 
is 10 -4- 60 = .166 amperes. But this is equally divided between 
two lines, so that each one receives .083 ampere or 83 milliamperes ; 
practically the same current as that given by the same battery to 
the single line. It will be seen that high line resistance and low 
battery resistance, relatively speaking, are required for the system. 
For this reason the storage battery is particularly available. The 
rule is that the resistance of the battery shall be less than the com- 
bined resistance of all the circuits worked by it. 

Unmarked End. The south-seeking pole of a magnet, so called 
because the other end, called the marked end, is usually marked 
with a scratch or notch by the maker, while the south pole is 
unmarked. 

V. (a) Symbol for velocity. 

(b) Symbol or abbreviation for volume. 

(c) Symbol or abbreviation for volt. 



STANDARD ELECTRICAL DICTIONARY. 557 

V. A. Symbol or abbreviation for voltaic alternatives, q. v. 

Vacuum. A space destitute of any substance. The great per- 
vading substance is in general sense the atmosphere. It is the 
gaseous mixture which surrounds and envelopes the earth and its 
inhabitants. It consists of a simple mixture of oxygen, 1 part, 
nitrogen, 4 parts, with 4 to 6 volumes of carbonic acid gas in 10,000 
volumes of air, or about one cubic inch to one cubic foot. It 
presses with a force of about 14.7 lbs. per square inch under the 
influence of the force of gravity. The term vacuum in practise 
refers to any space from which air has been removed. It may be 
produced chemically. Air may be displaced by carbonic acid gas 
and the latter may be absorbed by caustic alkali or other chemical. 
The air may be expelled and the space may be filled with steam 
which is condensed to produce the vacuum. Of course in all cases 
the space must be included in an hermetically sealed vessel, such as 
the bulb of an incandescent lamp. But the universal method of 
producing a vacuum is by air pumps. An absolute vacuum means 
the entire absence of gas or air, something almost impossible to 
produce. A high vacuum is sometimes understood to mean one 
in which the path of the molecules is equal in length to the diame- 
ter of the containing vessels, as in Crookes' Radiometer and other 
apparatus for illustrating the radiant condition of matter. The air 
left after exhaustion is termed residual air or residual atmosphere. 

Vacuum, Absolute. A space free of all material substance. It 
is doubtful whether an absolute vacuum has ever been produced. 

Vacuum, High. An approximate vacuum, so nearly perfect 
that the molecules of the residual gas in their kinetic motions 
rarely collide, and beat back and forth between the walls of the 
containing vessel, or between any solid object contained in the 
vessel and the walls of the vessel. The gas in such a vacuum is in 
the radiant or ultra-gaseous state. (See Ultra-gaseous Matter.) 

Vacuum, Low. A vacuum inferior to a high vacuum ; a 
vacuum in which the molecules collide with each other and do not 
move directly from side to side of the containing vessel. 

Vacuum, Partial. A space partially exhausted of air so as to 

contain less than an equal volume of the surrounding atmosphere. 
It really should come below a low vacuum, but is often treated as 
synonymous therewith. 

Vacuum, Torricellian. The vacuum existing above the mer- 
curial column in a barometer tube. The principle of this vacuum 
is applied in the Geissler and other air pumps. (See Pump, Geiss- 
ler — Pump, Sprengel — Pump, Swinburne,) 

Valency. The relative power of replacing hydrogen or com- 



55S STANDARD ELECTRICAL DICTIONARY. 

birring therewith possessed by different elements ; the number of 
atomic bonds belonging to any element. Thus oxygen has a two- 
fold valency, is bivalent or is a dyad, and combines with two atoms of 
hydrogen because the latter has a unitary atomicity, is monovalent 
or is a monad. 

Valve, Electrically Controlled. A valve which is moved by 
or whose movements are regulated by electricity. 

In the block system of railroad signaling the semaphores are 
worked by weights and pneumatic cylinders and pistons. The 
valves for admitting or releasing the compressed air are operated by 
coil and plunger mechanism. There are many other instances of 
the control of valves by the electric current. 

Vapor Globe. A protecting glass globe surrounding an incan- 
descent lamp, when the lamp is to be used in an atmosphere of 
explosive vapor, as in mines or similar places ; or when in a place 
where it is exposed to dripping water which would break the hot 
lamp bulb if it fell upon it. 

Variable Period. The period of adjustment when a current is 
started through a conductor of some capacity. It is the period of 
duration of the variable state, q. v., in a conductor. As indicated 
in the next definition in a cable of high electrostatic capacity a 
variable period of nearly two minutes may exist. This indicates 
the retardation in signaling to be anticipated in cables and other 
lines of high capacity. 

Variable State. When an electric circuit is closed the current 
starts through the conductor with its full strength from the point 
of closure, and advances with a species of wave front so that some 
time elapses before it attains its full strength in the most distant 
parts of the conductor, owing to its having to charge the conductor 
to its full capacity at the given potential. The state of the line 
while the current thus varies is called the variable state. 

A long telegraph line when a message is being transmitted may 
be always in the variable state. The current at the receiving end 
may never attain its full strength. 

In the case of such a conductor as the Atlantic cable, 108 seconds 
would be required for a current to attain t 9 q of its full strength at 
the distant end, and but ^ second to attain T ^j of its final value. 
During the period of increase of current the variable state exists. 

Variation of the Compass. The declination of the magnetic 
needle. (See Elements, Magnetic.) As the declination is subject to 
daily, annual and secular variations, it is unfortunate that this term 
is synonymous with declination. Thus the variation of the compass 
means its declination, while there is also the variation of the 



STANDARD ELECTRICAL DICTIONARY. 559 

declination and of other elements. The term variation of the com- 
pass is more colloquial than the more definite expression ' ' declina- 
tion," or " magnetic declination." 

Variometer. An apparatus used in determining the relative 
values of the horizontal component of the earth's magnetic field in 
different places. 

Varley's Condenser. A static condenser whose conducting 
surfaces are platinum electrodes immersed in dilute sulphuric acid. 
When the potential difference is ^th that of a Daniell's cell, two 
square inches of platinum have a capacity equal to that of an air 
condenser whose plates have an area of 80,000,000 square inches, and 
separated *^th of an inch from each other. As the E. M. F. in- 
creases the capacity also increases. 

Var ley's Resistances. Variable resistances formed of discs of 
carbonized cloth, q. v., piled up, and pressed together more or less 
firmly to vary the resistance as desired. 

Varnish. A glossy transparent coating of the nature of paint, 
applied as a protective, or ornamental coating to objects. 

Varnish, Electric. Alcoholic or etherial varnishes are the best 
for electrical apparatus. They dry quickly and perfectly, and tend 
to form surfaces unfavorable to the hygroscopic collection of 
water. Sealing wax dissolved in alcohol, or shellac dissolved in 
the same solvent are used for electrical apparatus, although the 
first is rather a lacquer than a varnish. Etherial solution of gum- 
copal is used to agglomerate coils of wire. It is well to bake var- 
nished objects to harden the coating. 

Varnish, Red. A solution of sealing wax in 90 per cent, alcohol. 
It is best made thin and applied in several coats, each coat being 
allowed to dry perfectly before the next is applied. It is often seen 
on Leyden jars. It is a protector from surface leakage. 

Vat. A vessel for chemical or other solutions. A depositing 
vat is one in which a plating solution is worked, for the deposition 
of electroplate upon articles immersed in the liquid, and electro- 
lyzed by an electric current. 

Velocity. The rate of motion of a body. It is usually expressed 
in distance traversed per second of time. The absolute unit is one 
centimeter per second or kine. The foot per second is very largely 
used also. 

The dimensions of velocity are length (L) divided by time (T) 
or L\T. 

Velocity, Angular. Velocity in a circle defined by the unit 
angle, or the angle which subtends a circular arc equal in length to 



560 STANDARD ELECTRICAL DICTIONARY. 

itself. The radius of the circle traversed by the moving body does 
not enter into this definition, as the real velocity of the object is not 
stated. If its angular velocity and the radius of the path it travels 
are given its actual velocity can be deduced. 

Velocity of Signaling. The speed of transmission of electric 
signals is affected by the nature of the line, as regards its static 
capacity, and by the delicacy of the receiving instruments, which 
may need a more or less strong current to be affected. Thus of an 
original current one per cent, may suffice to operate a sensitive 
instrument. This might give almost the velocity of light, while 
if the instrument would only respond to the full current nearly two 
minutes (see Variable State) might be required for the production 
of a signal. 

Velocity Ratio. A term applied to the ratios existing between 
the electrostatic and electro-magnetic units. If we take as numera- 
tors the dimensions of the different qualities in the electrostatic 
system, and their dimensions in the electro-magnetic system as 
denominators, the fractions thus obtained reduce to expressions 
containing only velocity or Fin some form. Thus if we divide 
the dimensions of the electrostatic quantity by the dimensions of 
electro-magnetic quantity the quotient is simply V ox velocity. A 
like division for potential, electrostatic and electro-magnetic gives 

i 
-y- y and so on. 

The value of the velocity ratio is very nearly 3 X io 10 (sometimes 
given as 2.98 X io 10 ) centimeters per second. This is almost 
exactly that of light (2.9992 X io 10 centimeters per second.) This 
is one of the proofs of Clerk Maxwell's magnetic theory of light. 
(See Maxwell 's Theory of Light.) 

Ventilation of Armature. In a dynamo or motor ventilation 
of the armature is often provided for by apertures through it in 
order to prevent heating. This heating is caused by Foucault 
currents. By proper disposition of the interior of the armature 
with properly disposed vanes and orifices an action like that of a 
fan blower can be produced, which by creating a current of air 
cools the machine very efficiently. 

Verticity, Poles of. Points upon the earth's surface where the 
horizontal component of magnetic force disappears, leaving only 
the vertical component active. The term is derived from the ver- 
ticity of the dipping needle when over either of them. 

Vibration Period. In electrical resonance the period of a vibra- 
tion in an electrical resonator. The length of this period indicates 
the quality of the resonator in responding to electrical oscillations 
by sympathetic vibration. For conductors of small resistance the 



STANDARD ELECTRICAL DICTIONARY. 561 

period is thus calculated. Let T be the period oi one-half a full 
vibration ; L the absolute coefficient of self-induction expressed in 
centimeters or in henries X 10- 9 ; C the electrostatic capacity of the 
terminals, also expressed in the same unit ; v the velocity of light 
in centimeters per second. Then we have the formula 

V 

Vibration, Sympathetic. A vibration in a cord or other body 
susceptible of elastic vibration produced by the vibrations of 
exactly the same period in a neighboring vibrating body. Thus if 
two tuning forks are tuned to precisely the same pitch, and are 
placed near each other, if one is sounded it will start the other into 
vibration by sympathy. 

In electricity its application is found in electric resonance experi- 
ments. The resonator has a definite period of electric resonance, 
and is made to give a spark by the exciter of identical period. 
This is by what may be called electric sympathetic vibration, and 
is exactly analogous to the action of the tuning forks upon each 
other. 

Vibrator, Electro=magnetic. The make and break mechanism 
used on induction coils, or other similar apparatus in which by 
alternate attractions by and releases from an electro-magnet an arm 
or spring is kept in motion. In most cases the work is done by a 
single magnet, whose armature is attracted to the magnet, when 
the latter is excited, but against the action of a spring which tends 
to pull it away from the magnet. In its motions a make and break 
action is produced, to give the requisite alternations of attraction 
and release. Two electro-magnets may be connected so as alter- 
nately to be excited and keep an arm carrying a mutual armature 
in vibration, or the same result may be attained by a polarized 
relay. The make and. break is illustrated under Bell, Electric — 
Coil, Induction — Anvil. 

Villari's Critical Value. Magnetization induced or residual in 
a wire is diminished on stretching, provided that the magnetiza- 
tion corresponds to an inducing force above a certain critical value, 
known as above; this being (Sir Wm. Thomson) about 24 times 
the terrestrial intensity. Below that critical value tension increases 
the magnetization of a magnetized wire. The effects of transverse 
expansive stress are opposed to those of longitudinal stretching. 
(Daniell.) 

Viole's Standard of Illuminating Power. A standard author- 
ized by the International Congress of 188 1. It is the light given by 
one square centimeter of platinum, melted, but just at the point of 



562 STANDARD ELECTRICAL DICTIONARY. 

solidification. It is equal to 20 English standard candles almost 
exactly. 

It has not been very widely accepted, the tendency among photo- 
metrists being to adhere to the old standards, carcel or candle. It 
is obvious that actual use of the Viole would be very inconvenient 
and would involve expensive apparatus, difficult to work with. 

Synonym — Viole. 

Vis Viva. The kinetic energy of a body in motion ; ' ' mechan- 
ical energy." 

Vitreous Electricity. Positive electricity ; the electricity pro- 
duced on the surface of glass by rubbing it with silk and other 
substances. (See Electrostatic Series,) 

The term ' * positive electricity ' ' should be allowed to supplant 
it. It is the analogue and opposite of resinous electricity. 

Vitriol, Blue. A colloquial or trade name for copper sulphate 
(CuSOJ. 

Vitriol, Green. A colloquial or trade name for ferrous sulphate 

(FeSOJ. 

Vitriol, White. A colloquial or trade name for zinc sulphate 
(Zn S0 4 ). 

Volt. The practical unit of electro-motive force or potential dif- 
ference. It may be referred to various data. 

An electro-motive force of one volt will cause a current of one 
ampere to flow through a resistance of one ohm. 

A condenser of one farad capacity charged with one coulomb 
will have a rise of potential of one volt. 

The cutting of 100,000,000 lines of force per second by a conductor 
induces one volt E. M. F. 

A Daniell's battery gives an E. M. F. of 1.07 volts ; about the 
most familiar approximate standard that can be cited. 

It is equal to ¥ ^ absolute electrostatic unit. 

It is equal to io 8 absolute electro-magnetic units. 

Voltage. Potential difference or electro-motive force expressed 
in volts ; as a voltage of 100 volts. Thus voltage may express the 
electro-motive force absorbed in a conductor, while electro-motive 
force is a term generally applied where it is produced, evolved or 
present in the object. The term voltage of a lamp expresses simply 
the volts required, but does not suggest the possession of electro- 
motive force. 

Voltage, Terminal. The voltage or potential difference at the 



STANDARD ELECTRICAL DICTIONARY. 563 

terminals of an electric current generator, such as a dynanio, as 
distinguished from the total electro-motive force of the dynamo or 
generator. 

In batteries the distinction is not generally made in practice ; 
the total electro-motive force of the battery is made the basis of 
calculations. 

Voltaic, adj. This adjective is used to qualify a great many 
things appertaining to or connected with current electricity. It is 
derived from Volta, the inventor of the voltaic battery, and now 
tends to displace the term " galvanic," formerly in general use. 

Voltaic Alternatives. A term used in electro-therapeutics or 
medical electricity to indicate an alternating battery current. 
Synonym — Alternative current. 

Voltaic Effect. The potential difference developed by contact 
of different conductors. It is the basis of the contact theory, q. v., 
of electricity, although it may be accepted as the expression for 
a condition of things by those who reject the above theory. This 
potential difference is slight when the conductors are separated, 
but it is calculated that it would be enormous could the metals be 
so quickly separated as to hold each its own charge. 

Thus if a copper and a zinc plate are assumed to be in contact, 
really -g-owToon centimeter or 5 ooooo0o inch apart, they may be 
treated as a pair of condenser plates. Being so near, their density 
of charge, which is a strongly bound charge, is enormous. If it were 
possible to separate them without permitting any discharge, their 
potential would rise by the separation, on the principle of Epinus' 
condenser, q. v., to such an extent that they would spark through 
twenty feet of air. (See Volta 's Fundamental Experiment.) 

Voltaic Electricity. Electricity of low potential difference and 
large current intensity ; electricity such as produced by a voltaic 
battery ; current or dynamic electricity as opposed to static elec- 
tricity. 

Voltameter. In general an apparatus for determining the quan- 
tity of electricity passing through a conductor by measuring the 
electrolytic action it can perform. 

Voltameter, Copper. An apparatus which may be of similar 
construction with the silver voltameter (see Voltameter ; Silver) , 
but in which a copper anode and a solution of copper sulphate are 
substituted for the silver anode and silver nitrate solution. One 
coulomb corresponds to .329 milligram or .005084 grain of copper 
deposited. It is not accepted as of as high a standard as the silver 
voltameter. 

The electrodes should be placed half an inch from each other. 



564 



STANDARD ELECTRICAL DICTIONARY. 



Two square plate electrodes may conveniently be used, and not 
less than two square inches on each plate should be the area per 
ampere of current. 

Voltameter, Differential, Siemens'. A volume or gas volta- 
meter with duplicate eudiometers and pairs of electrodes. It is 
used for determining the resistance of the platinum conductor used 
in his pyrometer. A current divides between the two voltameters ; 
in one branch of the circuit the platinum conductor is placed, in 
the other a known resistance. The current strength varying 
inversely with the resistance, the resistances of the two conductors 
are inversely proportional to the gas evolved. 

Voltameter, Gas. A voltameter whose indications are based on 
the electrolysis of water, made an electrolyte by the addition of 
sulphuric acid. The gases evolved are 
measured. It may take several forms. 

In one form it is an apparatus consist- 
ing of a single eudiometer or graduated 
glass tube with upper end closed and its 
lower end or mouth open, collecting the 
mixture of hydrogen and oxygen. 

In the form shown in the cut three 
tubes are connected, the side tubes repre- 
senting eudiometers. For each side tube 
there is a platinum electrode. In this 
apparatus the oxygen and hydrogen are 
connected in opposite tubes. A is an 
open tube filled with dilute sulphuric 
acid. By opening the cocks on B and C 
they can both be completely filled with 
acid. As shown in the cut, this operation 
is not yet completed. The hydrogen 
alone may in this case be measured. 

The mixed gas voltameter has only one 
eudiometer. 

The exact equivalents are only approxi- 
mately known. The volume of mixed 
gases per coulomb is given as . 1 738 cubic 
Fig. 341. Gas Voltameter, centimeters (Ayrton) ; .172 cubic centi- 
meters (Hospitaller) ; and other values by 
other authorities. The hydrogen is equal to % of the mixed gases 
almost exactly. 

Synonyms — Volume Voltameter — Sulphuric Acid Voltameter. 
The gas is measured at o° (32 F.) and 76 centimeters, or 30 inches 
barometer. 




STANDARD ELECTRICAL DICTIONARY. 565 

If the gas is measured in cubic inches, the temperature in degrees 
F., and the barometric height in inches, the following formula may 
be used for reduction to standard pressure and temperature. It is 
the volume corresponding to one coulomb. 

.0105S X 30 1491 — F.°— 32) 

h X 491 

For the metric measurements and degrees C. 

•I73S X 76 273 -C.° ) 

h X 273 

Voltameter, Silver. An apparatus consisting of a platinum 
vessel containing a solution of silver nitrate into which solution a 
silver anode dips, whose end is wrapped in muslin to prevent the 
detachment of any particles. When a current is passed by connect- 
ing one terminal to the dish and the other to the rod, securing a 
proper direction of current, silver will be deposited on the dish and 
the same amount will be dissolved from the rod. The dish is 
weighed before and after the test. Its increase in weight gives the 
silver deposited. 




In the cut Ag is the silver anode, Ptis the platinum dish, r is 
the conducting rod, p is a wooden standard, Cu is a copper plate on 
which the dish rests and which also serves as a conductor and con- 
tact surface, b is a muslin cloth to place over the silver plate to 
prevent detached particles falling in the dish ; 5 s / are the binding 
screws. 

The weight of silver corresponding to a coulomb is given variously 
by different authorities. Ayrton and Daniell take 1.11S15 milli- 



566 



STANDARD ELECTRICAL DICTIONARY. 



grams or .017253 grain of metallic silver. Other determinations 
are as follows : 

1. 1 183 milligrams (Kohlransch). 

1. 124 " (Merscart). 

The solution of silver nitrate should be from 15 to 30 per cent, of 
strength. The current should not exceed one ampere per six 
square inches ; or in other words not more than about T oVs grain of 
silver should be deposited per second on a square inch area of the 
dish. The edge of the silver disc or anode should be about equi- 
distant from the side and bottom of the dish. The latter notes are 
due to Lord Rayleigh. 

Voltameter, Weight. A voltameter in which the amount of 
decomposition is determined by weighing the products, or one of 
the products of the electrolysis. The titles Voltameter ', Copper \ 
and Voltameter ■, Silver, may be cited. 

In the cuts are shown examples of weight gas voltameters. These 
are tubes light enough to be weighed when charged. Each con- 





8^ c 

Fig"- 343- Weight Voltameters. 

tains a decomposition cell T, with its platinum electrodes, and 
charged with dilute sulphuric acid, while t is calcium chloride or 
other drying agent to collect any water carried off as vapor or as 



STANDARD ELECTRICAL DICTIONARY. 



567 



spray by the escaping gases ; c are corks placed in position when 
the weighing is being execnted, so as to prevent the calcium 
chloride from absorbing moisture from the air. 

In use the tubes are weighed. They are then connected to the 

circuit, after removal of the corks, and the decomposition proceeds. 

After a sufficient time they are removed, the corks put in place, 

and they are weighed again. The loss gives the water decomposed. 

The water corresponding to one coulomb is 

.09326 milligram .001430 grain, Ayrton, 

.092 " Hospitalier, 

.0935 " Daniell. 

Voltametric Law. The law on which voltameters are based. 
The amount of chemical decomposition produced by an electric 
current in a given electrolyte is proportional to the quantity of 
electricity passed through the solution. 

Volta's Fundamental Experiment. The moistened finger is 
placed on the upper plate of a condensing or electrophorous 




Fig. 344. Volta's Fundamental Experiment. 

electroscope. The other hand holds a plate of zinc z, soldered to 
a plate of copper c. The lower plate is touched with the copper. 
On removing the cover the gold leaves / diverge and with nega- 



568 STANDARD ELECTRICAL DICTIONARY. 

tive electricity. Hence zinc is supposed to be positively electrified 
when in contact with copper. The experiment is used to demon- 
strate the contact theory of electricity. 

Volta's Law of Galvanic Action. The electro-motive force 
between any two metals in an electro- chemical series (see Electro- 
Chemical Series) is equal to the sum of the electro-motive forces 
between all the intervening metals. 

Volta's Law of Thermo=electricity. In a compound circuit, 
consisting of a number of different metals, all points of which are 
at the same temperature, there is no current. 

Volt, B. A. The volt based on the B. A. ohm. It is equal to 
.9889 legal volt. 

Volt, Congress. The volt based upon the congress or legal 
ohm ; the legal volt. 

Volt=coulomb. The unit of electric work ; the watt-second ; it 
is equivalent to 

io 7 ergs. 
.24068 gram degree C. (calorie), 
•737337 foot lbs., 
.00134 horse power seconds. 

Volt Indicator. A form of easily read voltameter for use in 
electric light stations and for similar work. 

Volt, Legal. The legal volt based upon the legal ohm. It is 
equal to 1. 001 12 B. A. volt. 

Voltmeter. An instrument for determining the potential dif- 
ference of any two points. 

In many cases it is a calibrated galvanometer w r ound with a coil 
of high resistance. The object to be attained is that it shall receive 
only an insignificant portion of current, and that such portion 
shall suffice to actuate it. If connected in parallel with any portion 
of a circuit, it should not noticeably diminish its resistance. 

The divisions into which ammeters range themselves answer for 
voltmeters. In practice the same construction is adopted for both. 
The different definitions of ammeters in disclosing the general 
lines of these instruments are in general applicable to voltmeters, 
except that the wire winding of the coils must be of thin wire of 
great length. The definitions of ammeters may be consulted with 
the above understanding for voltmeters. 

In the use made of voltmeters there is a distinction from ammeters. 
An ammeter is a current measurer and all the current measured must 
be passed through it. But while a voltmeter is in fact a current 
measurer, it is so graduated and so used that it gives in its readings 



STANDARD ELECTRICAL DICTIONARY. 569 

the difference of potential existing between two places on a circuit, 
and while measuring the current passing through its own coils, it 
is by calibration made to give not the current intensity, but the 
electro-motive force producing such current. 

In use it may be connected to two terminals of an open circuit, 
when as it only permits an inconsiderable current to pass, it indi- 
cates the potential difference existing between such points on open 
circuit. Or it may be connected to any two parts of a closed 
circuit. Owing to its high resistance, although it is in parallel 
with the intervening portion of the circuit, as it is often connected 
in practice, it is without any appreciable effect upon the current. It 
will then indicate the potential difference existing between the two 
points. 

Voltmeter, Battery, A voltmeter for use in running batteries. 
In one form (Wirt's) it is constructed for a low range of voltage, 
reading up to two and a half volts and having exactly one ohm 
resistance, thus giving the battery some work to do. 

Voltmeter, Cardew. A voltmeter in which the current passing 
through its conductor heats such conductor, causing it to expand. 
Its expansion is caused to move an index needle. By calibration 
the movements of the needle are made to correspond to the poten- 
tial differences producing the actuating currents through it. The 
magnetic action of the current plays no part in its operation. It 
is the invention of Capt. Cardew, R. E. 

The construction of the instrument in one of its most recent 
forms is shown in the cut. On each side of the drum-like case of 
the instrument are the binding screws. These connect with the 
blocks m and //. To these the fine wire conductor is connected and 
is carried down and up over the two pulleys seen at the lowest 
extremity, its centre being attached to c. From c a wire is carried 
to the drum ft, shown on an enlarged scale on the left of the cut. 
A second wire from the same drum or pulley connects to the spring 
►S. The winding of the two wires is shown in the separate figure of 
c, where it is seen that they are screwed fast to the periphery of the 
little drum, and are virtually continuations of each other. By the 
screw A the tension of the spring Sis adjusted. 

On the shaft of the little dram ft is a pinion, which works into 
the teeth of the cog-wheel r. The shaft of r is extended through 
the dial of the instrument, and carries an index. The dial is 
marked off for volts ; g g and h h are standards for carrying the 
pulleys. 

The action of the instrument is as follows. The current passing 
through the wire heats it. This current by Ohm's law is propor- 
tional to the electro-motive force between the terminals. As it is 
heated it expands and as it cools contracts, definite expanding and 



57o 



STANDARD ELECTRICAL DICTIONARY. 



contracting corresponding to definite potential differences, As the 
wire expands and contracts the block or pin c moves back and forth, 
thus turning the drum p and cogwheel r one way or permitting it 
to turn the other way under the pull of the spring S. 




Fig. 345- Cardew Voltmeter. 

In this construction for a given expansion of the wire the piece 
c only moves one half as much. The advantage of using a wire 
twice as long as would be required for the same degree of move- 
ment were the full expansion utilized is that a very thin wire can 
be employed. Such a wire heats and cools more readily, and hence 
the instrument reaches its reading more quickly or is more dead- 
beat, if we borrow a phraseology properly applicable only to instru- 
ments with oscillating indexes. 

In the most recent instruments about thirteen feet of wire .0025 
inch in diameter, and made of platinum-silver alloy is used. 

If the potential differenceto be measured lies between 30 and 120 
volts the wire as described suffices. But to extend the range of the 



STANDARD ELECTRICAL DICTIONARY. 571 

instrument a resistance in series is required. If such resistance is 
double that of the instrument wire, and remains double whether 
the latter is hot or cold the readings on the scale will correspond 
to exactly twice the number of volts. This is brought about in 
some instruments by the introduction in series of a duplicate wire, 
precisely similar to the other wire, and like it, carried around 
pulleys and kept stretched by a spring. 

Thus whatever ratio of resistance exists between the two wires 
cold, it is always the same at any temperature, as they both increase 
in temperature at exactly the same rate. Tubes are provided to en- 
close the stretched wires and pulleys, which tubes are blackened. 

The voltmeter is unaffected by magnetic fields, and, as its self- 
induction is very slight, it is much used for alternating currents. 
The tubes containing the wire may be three feet long. 

Its disadvantages are thus summarized by Ayr ton. It absorbs a 
good deal of energy ; it cannot be constructed for small potential 
differences, as the wire cannot be made thicker, as it would make 
it more sluggish ; there is vagueness in the readings near the zero 
point and sometimes inaccuracy in the upper part of the scale. 

Volts, Lost. The volts at the terminals of a dynamo at full load 
fall short of their value on open circuit. The difference of the two 
values are termed lost volts. 

Voltmeter, Electrostatic. A voltmeter based on the lines of 
the quadrant electrometer. It includes two sets of quadrants, each 
oppositely excited by one of the two parts, whose potential differ- 
ence is to be determined. They attract each other against a con- 
trolling force as of gravity. 

One form has the two sets poised on horizontal axes, bringing the 
parts so that the flat quadrants move in vertical planes. 

In another form a number of quadrants are used in each set, the 
members of the two sets alternating with each other. One set is 
fixed, the others move and carry the index. 

Vulcanite. Vulcanized india rubber which by high proportion 
of sulphur and proper vulcanization has been made hard. It is 
sometimes distinguished from ebonite as being comparatively light 
in color, often a dull red, while ebonite is black. For its electrical 
properties see Ebonite. 

Both substances have their defects, in producing surface leakage. 

Washing with weak ammonia, or with dilute soda solution, fol- 
lowed by distilled water, is recommended for the surface, if there 
is any trouble with surface leakage. It may also be rubbed over 
with melted parafflne wax. 



572 STANDARD ELECTRICAL DICTIONARY. 

W. (a) A symbol or abbreviation for watt. 

(b) A symbol or abbreviation for work. 

(c) A symbol or abbreviation for weight. 

Wall Bracket. A telegraph bracket to be attached to the exter- 
nal walls of buildings to which wires are attached as they come 
from the poles to reach converters, or for direct introduction into 
a building. 

Wall Sockets. Sockets for incandescent lamps constructed to 
be attached to a wall. 

Ward. Direction in a straight line ; a term proposed by Prof. 
James Thompson. The words ''backward " and " forward " indi- 
cate its scope. 

Water. A compound whose molecule consists of two atoms of 
hydrogen and one atom of oxygen ; formula, H 2 O. 

Its specific gravity is i , it being the base of the system of specific 
gravities of solids and liquids. 

If pure, it is almost a non-conductor of electricity. If any im- 
purity is present it still presents an exceedingly high, almost 
immeasurable true resistance, but becomes by the presence of any 
impurity an electrolyte. 

Water Equivalent. In a calorimeter of any kind the weight of 
water which would be raised as much as is the calorimeter with its 
contents by the addition of any given amount of heat received by 
the calorimeter. 

Waterproof Lamp Globe. An outer globe for incandescent 
lamps, to protect them from water. 

Watt, (a) The practical unit of electric activity, rate of work, 
or rate of energy. It is the rate of energy or of work represented 
by a current of one ampere urged by one volt electro-motive force ; 
the volt-ampere. 

It is the analogue in electricity of the horse power in mechanics ; 
approximately, 746 watts represent one electric horse power. 

Ohm's law, taken as C = E/R, gives as values for current, C 
and E/R, and for electro-motive force C R. In these formulas, C 
represents current strength, R represents resistance and E repre- 
sents electro-motive force. Then a watt being the product of 
electro-motive force by current strength, we get the following 
values for rate of electric energy, of which the watt is the practical 
unit: (1) E 2 /R — (2) C E — (3) C 2 R. 

The equivalents of the watt vary a little according to different 



STANDARD ELECTRICAL DICTIONARY. 573 

authorities. Ayrton gives the following equivalents : 44.25 foot 
pounds per minute-. 7375 foot pounds per second — -^ horse power. 
These values are practically accurate. Hospitaller gives .7377 foot 
pounds per second. Hering gives .737324 foot pounds per second, 



7 4 5 9 4 1 

It is equal to io T ergs per second. 

Synonym — Volt-anipere. 

[c\ It has leen proposed to use the term as the unit of energy, 
instead of activity or rate of energy (Sir C. W. Siemens, British 
Association, 1882) ; this use has not been adopted and may be 
regarded as abandoned. 

Watt=hour. A unit of electric energy or work ; one watt 
exerted or expended for one hour. It is equivalent to : 
866.448 gram-degrees C. (calories) 
2654.4 foot lbs. 

3600 watt-seconds or volt-coulombs. 

60 watt-minutes. 

Watt=minute. A unit of electric energy or work ; one watt 
exerted or expended for one minute. 
It is equivalent to 

14.4408 gram-degrees C. (calories), 
44.240 foot pounds, 
60 watt seconds or volt-coulombs, 

g 1 ^ watt hour. 

Watts, Apparent. The product in an alternating current 
dynamo of the virtual amperes by the virtual volts. To give the 
true watts this product must be multiplied by the cosine of the 
angle of lead or lag. (See Current, Wattless.) 

Watt=second. A unit of electric energy or work. One watt 
exerted or expended for one second. 
It is equivalent to 

.24068 gram degree C. (calorie), 

.000955 lb. degree F., 

•757537 foot lbs., 

.0013406 horse power second (English), 

.0013592 horse power second (metric). 
Synonym — Volt-coulomb. 

Waves, Electro=magnetic. Ether waves caused by electro- 
magnetic disturbances affecting the luminiferous ether. (See 
Discharge, Oscillatory — Maxwell's Theory of Light — Reso?iance i 
Electric.) 



574 



STANDARD ELECTRICAL DICTIONARY. 



Weber, (a.) A name suggested by Clausius and Siemens to 
denote a magnet pole of unit strength. This use is abandoned. 

(b.) It has been used to designate the unit of quantity — the 
coulomb. This use is abandoned. 

(c.) It has been used to designate the unit of current strength — 
the ampere. This use is abandoned. 

Weber=meter. An ampere-meter or ammeter. The term is 
not used since the term "weber," indicating the ampere or cou- 
lomb, has been abandoned. 

Welding, Electric. Welding metals by heat produced by 
electricity. The heat may be produced by a current passing 
through the point of junction (Elihu Thomson) or by the voltaic 
arc. (Benardos & Olzewski.) 




Fig. 346. Electric Welding Induction Coil. 

The current process is carried out by pressing together the ob- 
jects to be united, while holding them in conducting clamps. A 
heavy current is turned on by way of the clamps and rapidly heats 
the metals at the junction, which is of course the point of highest 
resistance. As the metal softens, it is pressed together, one of the 
clamps being mounted with feed motion, flux is dropped on if 
necessary, and the metal pieces unite. 

The most remarkable results are thus attained ; almost all 
common metals can be welded, and different metals can be welded 



STANDARD ELECTRICAL DICTIONARY. 575 

together. Tubes and other shapes can also be united. In many 
cases the weld is the strongest part. 

The alternating current is employed. A special dynamo is some- 
times used to produce it. This dynamo has two windings on the 
armature. One is of fine wire and is in series with the field 
magnets and excites them. The other is of copper bars, and 
connects with the welding apparatus, giving a current of high 
intensity but actuated by low potential. 

Where the special dynamo is not used, an induction coil or 
transformer is used. The primary includes a large number of con- 
volutions of relatively fine wire ; the secondary may only be one 
turn of a large copper bar. 

The cut shows in diagram an electric welding coil. P is the 
primary coil of a number of turns of wire ; 5 5 is the secondary, a 
single copper bar bent into an almost complete circle. It terminates 
in clamps D D for holding the bars to be welded. B C, B / O are 
the bars to be welded. They are pressed together by the screw 
J. The large coil / of iron wire surrounding the coils represents 
the iron core. 

The real apparatus as at present constructed involves many 
modifications. The diagram only illustrates the principle of the 
apparatus. 

In welding by the voltaic arc the place to be heated is made an 
electrode of an arc by connection with one terminal of an electric 
circuit. A carbon is connected to the other terminal. An arc is 
started by touching and withdrawal of the carbon. The heat may 
be used for welding, soldering, brazing, or even for perforating or 
dividing metal sheets. 

Welding Transformer. The induction coil or transformer 
used in electric welding. For its general principles of construction, 
see Welding, Electric. 

Wheatstone's Bridge. A system of connections applied to 
parallel circuits, including resistance coils for the purpose of 
measuring an unknown resistance. A single current is made to 
pass from A through two parallel connected branches, joining 
together again at C. A cross connection B D has a galvanom- 
eter or other current indicator in circuit. In any conductor 
through which a current is passing, the fall of potential at given 
points is proportional to the resistance between such points. 
Referring to the diagram a given fall of potential exists between 
A and C. The fall between A and B is to the fall between 
A and C as the resistance r between A and B is to the resistance 
r -\- r r between A and C. The same applies to the other branch, 
with the substitution of the resistances s and s / and the point D 



576 



vSTANDARD ELECTRICAL DICTIONARY. 



for r r f and B. Therefore, if this proportion holds, r : r f : : 5 : s'. 
No current will go through B D , and the galvanometer will be 
unaffected. Assume s / to be of un- 
known resistance, the above proportion 
will give it, if r, r' and 5 are known, 
or if the ratio of r to r' and the abso- 
lute value of s is known. In use the 
resistances r, r' % and 5 are made to 
vary as desired. To measure an un- 
known resistance it is introduced at 
s / 9 and one of the other resistances is 
varied until the galvanometer is un- 
affected. Then the resistance of s / is 
determined by calculation as just ex- 
plained. The artificial resistances may 
be resistance coils y q. v., or it is enough 
to have one unknown resistance at s. 
Then if the length of wire A B C is 
, accurately known, the point B can be 
shifted along it until the balance is at- 
tained. The relative lengths A B, and 
B C y will then give the ratio r : r f 
needed for the calculation. This assumes the wire A B C to be 
of absolutely uniform resistance. This is the principle of the 
meter-bridge described below. The use of coils is the more corn- 




Fig- 347- 

Wheatstone Bridge 

Connections. 





^Mm mCi 



Fig. 348. Top of Box Bridge. 

mon method and is carried out by special resistance boxes, with 
the connections arranged to carry out the exact principle as 



STANDARD ELECTRICAL DICTIONARY. 577 

explained. The principle of construction and use of a resistance 
box of the Wheatstone bridge type, as shown in the cut, is described 
under Box Bridge, q. v. 

The next cut shows the sliding form of bridge called the meter 
bridge, if the slide wire is a meter long, or a half- or a quarter- 
meter bridge, etc., according to the length of this wire. It is 




Fig. 349. Meter Bridge. 

described under Meter Bridge, q. v. Many refinements in con- 
struction and in proper proportion of resistances for given work 
apply to these constructions. 

Synonyms — Electric Balance — Resistance Bridge — Wheatstone's 
Balance. 

Whirl, Electric, (a) A conductor carrying an electric current 
is surrounded by circular lines of force, which are sometimes termed 
an electric whirl. 

{6) The Electric Flyer. (See Flyer, Electric.) 

Wimshurst Electric Machine. An influence machine for 
producing high potential or static electricity. 

Two circular discs of thin glass are mounted on perforated hubs 
or bosses of wood or ebonite. Each hub has a groove turned upon 
it to receive a cord. Each disc is shellacked. They are mounted 
on a horizontal steel spindle so as to face and to be within one- 
eighth of an inch of each other. On the outside of each disc six- 
teen or eighteen sectors of tinfoil or thin metal are cemented. 



578 



STANDARD ELECTRICAL DICTIONARY. 



Two curved brass rods terminating in wire brushes curved into a 
semi-ellipse just graze the outer surfaces of the plates with their 
brushes. They lie in imaginary planes, passing through the axis of 
the spindle and at right angles from each other. 

Four collecting combs are arranged horizontally on insulating 
supports to collect electricity from the horizontal diameters of the 
discs. These lie at an angle of about 45 ° with the other equalizing 
rods. Discharging rods connect with the collecting combs. 

The principle of the machine is that one set of sector plates act 
as inductors for the other set. Its action is not perfectly under- 
stood. 

It works well in damp weather, far surpassing other influence 
machines in this respect. On turning the handle a constant suc- 
cession or stream of sparks is produced between the terminals of 
the discharging rods. 

Windage. In a dynamo the real air gap between the armature 
windings and pole pieces is sometimes thus termed. 

Wind, Electric. The rush of air particles from a point con- 
nected to a statically charged condenser. 

Winding, Compound. A method of winding a generator or 
motor in which a shunt winding is used for the field magnets and 
in which also a second winding of the magnet is placed in series 
with the outer circuit. (See Winding, Series— Winding , Shunt.) 




& Ohms £ x 

Fig- 35°- Characteristic Curves of Shunt and Series Winding. 

The object of compound winding is to make a self-regulating 
dynamo and this object is partly attained for a constant speed. 

The characteristic curves of shunt and series winding are of oppo- 
site natures. The first increases in electro-motive force for resist- 
ance in the outer circuit, the latter decreases under the same 



STANDARD ELECTRICAL DICTIONARY. 579 

conditions. If the windings are so proportioned that these con- 
ditions for each one of the two windings are equal and opposite, 
it is evident that the characteristic may be a straight line. This, 
however, it will only be at a single speed of rotation. 

Winding, Disc. A winding which (S. P. Thompson) may be 
treated as a drum winding extended radially, the periphery corre- 
sponding to the back end of the drum. The magnet poles are 
generally placed so as to face the side or sides of the disc. 

Winding, Lap. A method of winding disc and drum armatures. 
It consists in lapping back each lead of wire towards the preceding 
lead upon the commutator end of the armature. Thus taking the 
letter U as the diagrammatical representation of a turn of wire in 
connecting its ends to the commutator bars they are brought 
towards each other so as to connect with contiguous commutator 
bars. This carries 'out the principle of keeping the two members of 
the U moving in regions of opposite polarity of field, so that the 
currents induced in them shall have opposite directions, thus pro- 
ducing a total current in one sense through the bent wire. 

Winding, Long Shunt. A system of compound winding for 
dynamos and motors. The field is wound in series and, in addition 
thereto, there is a shunt winding connected across from terminal to 
terminal of the machine, and which may be regarded either as a 
shunt to the outer circuit, or as a shunt to the series-field and 
armature winding. (See Winding, Short Shunt.) 

Synonyvis — Series and Long Shunt Winding. 

Winding, Multiple. A winding of an electro-magnet, in which 
separate coils are wound on the core, so that one or any number 
may be used as desired in parallel or in series. For each coil a 
separate binding post should be provided. 

Winding, Multipolar. Winding adapted for armatures of multi- 
polar dynamos or motors. 

Winding, Series. A method of winding a generator or motor, 
in which one of the commutator-brush connections is connected to 
the field-magnet winding ; the other end of the magnet winding 
connects with the outer circuit. The other armature-brush con- 
nects with the other terminal of the outer circuit. 

Winding, Series and Separate Coil. A method of automatic 
regulation applied to alternating current dynamos. 

Winding, Short Shunt. A method of compound winding 
for dynamos and motors. The field is wound in series, and in 
addition thereto there is a shunt winding connected from brush 



580 STANDARD ELECTRICAL DICTIONARY. 

to brush only, thus paralleling the armature. (See Winding, Long 
Shunt.) 

Synonyms — Series and Short Shunt Winding. 

Winding, Shunt. A method of winding a generator or motor. 
Each commutator-brush has two connections. One set are the 
terminals of the outer circuit, the other set are the terminals of 
the field-magnet windings. In other words, the field-magnet wind- 
ings are in shunt or in parallel with the outer circuit. 

Winding, Shuttle. A method of dynamo or motor-armature 
winding. A single groove passes longitudinally around the core 
and in this the wire is continuously wound. The system is not 
now used. The old Siemens' H armature illustrates the principle. 

Winding, Wave. A method of winding disc and drum arma- 
tures. It consists in advancing the commutator ends of the U 
shaped turns progressively, so that as many commutator bars 
intervene between any two consecutive commutator connections of 
the wire as there are leads of wire on the drum between consecu- 
tive leads of the wire. This is carried out with due regard to the 
principle that taking the letter U as the diagrammatical representa- 
tion of a turn of wire, its two members must move through regions 
of the field of opposite polarity. 

Wire Finder. A galvanometer or other instrument used for 
identifying the ends of a given wire in a cable containing several. 

Work. When a force acts upon a body and the body moves in 
the direction of the force, the force does work. Hence, work is 
the action of a force through space against resistance. 

It is generally expressed in compound units of length and weight, 
as foot-pounds, meaning a pound raised one foot. 

Work, Electric, Unit of. The volt-coulomb, q. v., or watt- 
second, as it is often termed. 

Working, Diode. In multiplex telegraphy the transmission 
of two messages, simultaneously, over one wire. (See Telegraphy, 
Multiple.) 

Working, Contraplex. A variety of duplex telegraphy in which 
the messages are sent from opposite ends of the line, simultane- 
ously, so as to be transmitted in opposite directions. (See Work- 
ing, Diplex.) 

Working, Diplex. In duplex telegraphy the sending of two 
independent messages from the same end of the line in the same 
direction. 



STANDARD ELECTRICAL DICTIONARY. 581 

Working, Double Curb. A method of working telegraph lines. 
When a signal is sent the line is charged. This has to be got rid 
of, and is an element of retardation. In double curb working it is 
disposed of by sending a momentary current first in the reverse, 
and then in the same, and finally in the reverse direction. This is 
found to reduce the charge to a very low point. 

Working, Hexode. In multiplex telegraphy the transmission 
of six messages simultaneously over one wire. (See Telegraphy , 
Multiplex .) 

Working, Pentode. In multiplex telegraphy the transmission 
of five messages simultaneously over one wire. (See Telegraphy, 
Multiplex.) 

Working, Reverse Current. A method of telegraphy, in which 
the currents are reversed or alternated in direction. 

Working, Single Curb. A simpler form of telegraph signal- 
ing than double curb working. It consists in sending a reverse 
current through the line for each signal by reversing the battery 
connection. 

Working, Tetrode. In multiplex telegraphy the transmission 
of four messages simultaneously over the same line. (See Teleg- 
rap hy , Mu I tip I ex . ) 

Working, Triode. In multiplex telegraphy the transmission of 
three messages simultaneously over the same wire. (See Teleg- 
raphy, Multiplex ■.) 

Work, Unit of. The erg, q. v. It is the same as the unit of 
energy, of which work is the corelative, being equal and opposite 
to the energy expended in doing it. 

There are many other engineering units of work, as the foot- 
pound and foot- ton. 

Yoke. In an electro-magnet, the piece of iron which connects 
the ends furthest from the poles of the two portions of the core on 
which the wire is wound. 

Zamboni's Dry Pile. A voltaic pile or battery. It is made 
of discs of paper, silvered or tinned on one side and sprinkled on 
the other with binoxide of manganese. Sometimes as many as 
2, 000 of such couples are piled up in a glass tube and pressed 
together with two rods which form the terminals. They maintain 
a high potential difference, but having very high resistance and 
slight polarization capacity, give exceedingly small quantities. 

Zero, (a) The origin of any scale of measurement. 
[d) An infinitely small quantity or measurement. 



582 STANDARD ELECTRICAL DICTIONARY. 

Zero, Absolute. From, several considerations it is believed that 
at a certain temperature the molecules of all bodies would touch 
each other, their kinetic motion would cease, and there would be 
no heat. This temperature is the absolute zero. It is put at — 273 
C. (-459° P.) 

Zero, Potential. Conventionally, the potential of the earth. 

True zero potential could only exist in the surface of a body 
infinitely distant from other electrified bodies. 

Zero, Thermometric. There are three thermometric zeros. 
In the Reaumur and centigrade scales, it is at the temperature of 
melting ice ; in the Fahrenheit scale, it is32° F. below that temper- 
ature, or corresponds to — 17.78 C. 

The third is the absolute zero. (See Zero, Absolute.) 

Zinc, A metal; one of the elements; atomic weight, 65.1; 
specific gravity, 6.8 to 7.2. 

microhms. 
Resistance at o° C. (32 F.), per centimeter cube, 5.626 

Resistance at o° C. (32 F.), per inch cube, 2.215 

Relative resistance (silver =1), 3-741 

ohms. 
Resistance of a wire, 1 foot long, weighing 1 grain, .5766 
[a) 1 foot long, 1 millimeter diameter, 33-85 

\b) 1 meter long, weighing 1 gram, -4023 

<c) 1 meter long, 1 millimeter diameter, -07163 

Zinc is principally used in electrical work as the positive plate in 
voltaic batteries. 

Zincode. The terminal connecting with the zinc plate, or its 
equivalent in an electric circuit ; the negative electrode ; the 
kathode. A term now little used. 

Zinc Sender. An apparatus used in telegraphy for sending a 
momentary reverse current into the line after each signal, thus 
counteracting retardation. 

Zone, Peripolar. In medical electricity, the region surround- 
ing the polar zone, q. v. 

Zone, Polar. In medical electricity, the region surrounding 
the electrode applied to the human body. 



APPENDIX 

Consult Special Index to this Appendix, immediately 
following the general index. 



Absorption, Luminous. The retention of part of the energy of 
light in its passage through bodies not absolutely transparent. 
Absorption of Electric Light by Globes. 
Kind of Glass. Per cent, absorbed. 

Clear, 10 to 20 

Alabaster, 15 " 25 

Opal, 20 " 30 

Ground, 30 " 40 

• Heavily ground, 40 " 50 

Heavy opal, 50 " 60 

Large globes absorb more light than small ones. 

(Geipel & Kilgour and von Hefner-Alteneck.) 

Adhesion, Electric. Adhesion between bodies due to the attrac- 
tion of their dissimilar electrostatic charges. 

Admittance. The reciprocal of impedance, q. v. It is expressed 
in mhos. 

A. I. E. E. An abbreviation for American Institute of Electrical 
Engineers, a corporate body of electricians with headquarters in 
New York City. It is the foremost electrical society of the Western 
Hemisphere. 

Alternator, Diphase. A dynamo electric machine which gen- 
erates two alternating E. M. F.'s separated by a quarter cycle, or 
in quadrature. 

Synonym — Diphaser. 

Alternator, Monocyclic. An alternator in which the uniphase 
and triphase systems are combined. 

The armature is wound with two circuits, one of which generates 
the principal E. M. F. for uniphase transmission ; while the other 
circuit, of smaller wire, is connected to the middle of the main 
winding and generates an E. M. F. in quadrature with the main 
winding. 



584 STANDARD ELECTRICAL DICTIONARY. 

The main winding is connected to the lighting circuits in the 
the usual manner. For operating triphase motors a third, or power, 
wire is connected to the auxiliary winding and led to the middle of 
two transformers in series on the Uniphase circuit. The secondary 
circuits of the transformers are connected in series, the secondary of 

le, however, being connected in the reverse sense. Three wires 
leading from these secondaries furnish a triphase current to the 
motors. 

Alternator, Multiphase. A dynamo electric machine which 
generates two or more alternating currents in definite phase rela- 
tionship with each other. They are required when it is desired to 
operate alternating current motors which have to start under full 
load. 

Synonym — Multiphaser. 

Alternator, Triphase. A dynamo electric machine which 
generates three separate alternating E. M. F.'s separated by one- 
third of a cycle. 

Synonym — Triphaser. 

Alternator, Uniphase. A dynamo electric machine which gen- 
erates a simple alternating current. 
Synonym — Uniphaser. 

Ammortisseur. A device proposed by Hutin and Leblanc to 
compensate armature reaction and deaden sparking at the brushes 
of a dynamo. It consists of a series of rods of copper carried 
through slots in the pole faces and short-circuited together at the 
ends by two rings of copper. The arrangement constitutes a 
damper for oscillations of the magnetic flux at commutation. 

Ampere, International. The legal unit of current defined by 
the International Congress at Chicago in 1893. 

It is one tenth of the unit of current of the C. G. S. system of 
electro-magnetic units, and it is represented sufficiently well for 
practical use by the unvarying current which, when passed through 
a solution of nitrate of silver in water, and in accordance with cer- 
tain specifications, deposits silver at the rate of 0.001118 of a gram 
per second. 

Amyloid. A substance used for incandescent lamp filaments. 
Its composition is C 6 H 10 5 . 

Analogy, Hydraulic. A method used to illustrate and explain 
electrical phenomena in a popular way by showing the similarity 
between certain electrical and hydraulic actions. For instance, — 
a dynamo charging a storage cell is like a pump filling a tank, etc. 
(See Ampere.) 



STANDARD ELECTRICAL DICTIONARY. 585 

Anchoring of Trolley Line. A method cf sustaining a trolley 
wire against longitudinal strains by means of guys attached to the 
wire and stretched in opposite directions. 

Anchor Pole. A pole of sufficient stiffness to assume the entire 
tension of all its circuits. It is used where an abrupt angle occurs, 
or where a heavy line is terminated to enter underground conduits. 

Anode, Preponderating. In an induction coil the induced 
E. M. F. is greater when the primary current is broken than when 
it is made. The positive terminal of this greater E. M. F. is the 
preponderating anode. The opposite terminal is called the pre- 
ponderating cathode. 

Anticathode. Whatever substance is struck by the cathodic 
stream in a Crookes' tube. The X-rays apparently emanate from 
the anticathode. 

Anti=Hum. A galvanized iron shackle inserted directly in a 
telegraph line wire, near a pole, and provided with a washer, or 




Fig. 351. Anti-Hum. 

cushion, of rubber or other suitable material to take up the vibra- 
tions of the wire. To preserve the continuity of the circuit a piece 
of wire called a bridle or jumper is passed loosely around the anti- 
hum and soldered to the main line at both ends. 

Arc Deflector. An electro-magnet, with a peculiarly-shaped 
pole piece, used in an electric railway motor controller to power- 
fully deflect, and thereby extinguish, the arcs formed on breaking 
the various contacts when the controller cylinder is turned. 

Armature, Toothed Ring. A ring armature whose core has 
projections between which the coils are wound. 

Arm Rest. A device for lessening the fatigue of holding a tele- 
phone receiver to the ear. It consists of a bracket carrying a pad 
or cushion on which the elbow is supported. 

Synonym — Elbow Rest. 

Auto=Transformer. A transformer containing but one coil of 
wire on an iron core. There are three terminals, one at each end 
of the coil and one connected to it at an intermediate point. 



586 STANDARD ELECTRICAL DICTIONARY. 

When used as a pressure reducer the whole coil is connected as a 
primary and the part coil as a secondary. Connecting in the oppo- 
site sense will make it act as an augmentator of pressure. 

Synonym— One-Coil Transformer. 

§@. The symbol for the unit of flux-density, the gauss, q.v. 

Balanced Metallic Circuit. A metallic circuit whose two sides 
are electrically similar. 

Balance Indicator. An instrument used on the Edison three- 
wire system to show if the potentials on the two sides of the system 
are equal. It consists of two equal high resistances connected in 
series to the two outside wires; a simple galvanometer connected to 
the junction between the high resistances and to the neutral wire 
shows any inequality of potentials. 

Ball Lightning. {See Lightning, Globe.) 




Fig. 352. Wire Barrow. 

Barrow, Wire. A hand barrow provided with a reel on which 
a coil of wire may be placed. 
It is used in stringing pole lines. 

Bar, Tamping. An iron bar with an end shaped suitably for 
ramming or beating down the soil, stones, etc., around the butt of 
a pole when the hole in which it rests is being filled up. 

Baton, Electric. An orchestra conductor's baton arranged so as 
to close an electric circuit at each stroke of beating time. It is 
used in physiological experiments in connection with a chrono- 
graph to determine accuracy of rhythmic action. 

An electrically illuminated baton has been used in the opera so 
as to be visible to the orchestra when the auditorium lights are 
extinguished during change of scene. 

Bipolar. Adj. Having two poles. 

Bismuth Spiral. An instrument for the measurement of strong 
magnetic fields. Its operation depends on the fact that the resist- 
ance of bismuth varies about 5 per cent, for a change of 1000 lines 
of force in a magnetic field. 



STANDARD ELECTRICAL DICTIONARY. 587 

Bond, Rail, A means of obtaining good and ample electrical 
connection between adjoining rail ends in order that the return 
current in an electrical railway system may be led back to the power 
station without undue leakage through the earth. 

Booster. A dynamo placed in series with an electric circuit 
so as to raise its E. M. F. 

It is used in multiple arc systems of electrical distribution to 
increase the E. M. F. so as to charge a storage battery, or to feed 
more current into the conductors at points of low E. M. F. (See 
Dynamo, Equalizing — Dynamo, Far Leading.) 

Synonym — Compensator. 

Border Lights, Rows of lights located in a reflector and sus- 
pended between the curtains in the flies of a theater stage. 

Boucherizing Process. A method invented by August Bouch- 
erie (1801-1871) for the prevention of decay in telegraph poles, etc., 
by impregnation with a solution of copper sulphate. 

Brace, Cross Arm. A strengthening support for a heavily 
loaded cross arm. 

Break=Wheel. A wheel provided at its periphery with alter- 
nate insulating and conducting segments. A pair of brushes bear- 
ing on the periphery carry the current to be interrupted. 

When used to break the primary circuit of an induction coil, a 
condenser or an air blast is used to lessen sparking and produce a 
quick break. [See Air Blast (b.)~\ 

A simple form of break wheel with segments of various lengths 
is used to transmit signals automatically in messenger and fire 
alarm call boxes. 

Bridges. Heavy conductors in a direct current incandescent 
lighting station leading from the dynamos, overhead to the switch 
board. 

Bridge, Decade. A Wheatstone bridge in which the rheostat 
coils are arranged in groups often equal coils of each denomination 
connected in series. This allows of the comparison of, say, the ten 
unit coils with the one ten coil, etc. ; and has the advantage that 
the number of plugs used is constant. 

B. T. U. (a) An abbreviation for Board of Trade Unit, the com- 
mercial unit of electrical work adopted by the British Board of 
Trade. 

It is the kilowatt-hour. 

(b) An abbreviation for British Thermal Unit, the amount of 
heat required to raise a pound of water i° F. It equals 776 foot- 
pounds. 



588 



STANDARD ELECTRICAL DICTIONARY. 



Bunch Lights. A group of incandescent lamps placed in a 
reflector which is mounted on a portable iron stand and provided 
with a flexible cable and attaching plug. They are used for light- 
ing any particular part of a scene on a theater stage. 

Burnettizing Process. A method invented by Sir William 
Burnett for the prevention of decay by impregnation with a solu- 
tion of zinc chloride. 

It is used for preserving telegraph poles, etc. 

Bushed Poles. A method of diminishing the fringing of lines 
of magnetic force at the edge of dynamo pole pieces by bushing 
the armature chamber with a thin iron tube 
which acts as a carrier of the stray magnetism 
between the pole tips. 

Bushing, Socket. A nozzle of insulating ma- 
terial screwed into the base of an incandescent 
lamp socket for the purpose of insulating the 
socket from a fixture or, in the case of pendants, 
to protect the flexible cord from abrasicn. 

Button, Ceiling. A perforated block of insulating material 
fastened to the ceiling and having a pendant cord passing through 
it so that the pendant may hang from a different point than its ceil- 
ing rosette. 




Fig. 353. Flat 
Socket Bushing. 




Fig. 354. Ceiling Button. 



Cable, Beaded. A cable devised to have a low electrostatic 
capacity. Instead of rubber or gutta percha, the wires are incased 
in a series of wooden beads and then placed in a leaden sheath. 

Cable, Emergency. A light cable of about half a mile in length 
used to temporarily repair a line broken by storm, wash-out, or 
other accident. 

Cablegram. A telegraphic dispatch which has been transmitted 
through a submarine cable. 



STANDARD ELECTRICAL DICTIONARY. 



5§9 



Cable Head. A cast-iron box provided with binding posts and 
arranged to form a water-tight connection box at the terminal of a 
cable. 

Call Box, District. A box containing mechanism for automatic- 
ally sending signals to a messenger office. 





Balance. 

Candle Balance. A scale beam arranged to hold one or two 
standard candles in a photometer so as to determine their loss of 
weight while burning for any given time. (See Candle Power.) 

Canopy. An ornamental metal shell 
placed at the base of a lighting fixture for 
the purpose of concealing the insulating 
joint, cut-out, etc. 

Can t= Hook. A wooden lever with an 
iron hook hinged near one end. It is used 
Fig. 356. Canopy. for rolling logs and for turn j ng telegraph 

poles, when first set in their holes, so that the cross-arm gains will 
face properly. 

Capability, Electrical, of Voltaic Cell. The square of its 
E. M. F. divided by its internal resistance. It represents the 
activity, in watts, of the cell when short circuited. If an activity 
of P watts is required from a given battery, the minimum number 
of cells required will be 4 P-i-the capability of one cell. (Houston 
and Kennelly.) 

Carbon Back. A block of carbon used as the rear, non- vibrating 
electrode of a telephone transmitter. 

Carbon Balls. Spheres of carbon for use in certain forms of 
telephone transmitters. The balls are sometimes placed so as to 
complete the circuit between a carbon diaphragm and a carbon back 
having cavities in which the balls partly lie. 

Carbon Button. A small disc of compressed lamp-black. Its 
property of having a variable electrical resistance under varying 
pressure fits it for use in certain forms of telephone transmitters. 



590 STANDARD ELECTRICAL DICTIONARY. 

Carbon Diaphragm. A disc of carbon about -^ inch thick used 
as the front, vibrating electrode of a telephone transmitter. 

Carcass of Dynamo. The field magnet frame of a dynamo. 

Cathetometer. An instrument for accurately measuring differ- 
ences of level between near points. It consists of a vertical bar on 
which a divided scale is engraved. This bar carries a sliding tele- 
scope provided with cross -hairs. The points whose difference of 
level is required are observed through the telescope, and the posi- 
tions of the latter on the scale enable the relative heights to be 
easily calculated. The addition of another telescope to the bar 
adapts the instrument to be used in the comparison of standards 
of length. Cathetometers are not usually constructed of a greater 
vertical range than 150 centimeters. 

Cathode. The same as Kathode, q. v. 

Cathode, Preponderating. (See Appendix, Anode, Preponder- 
ating.) 

Catoptrics. The science of the reflection of light. 

Cazin. A unit of electro-chemical energy proposed by F. M. F. 
Cazin, and defined by him as "the unit of chemical energy and 
work, which is consumed, when one decigram atomic-weight of 
oxygen (negative matter) combines with a positive element, which 
unit is the equivalent of the electrical force, which in electrolytic 
action deposits, per second, 200 ampere-quantities of metal." 

Cell, Heat. A voltaic cell in which heat energy is converted 
into electrical energy. They are of three principal varieties : (a) 
Those in which the heat acts upon the materials of the cell by 
causing fusion or decomposition, (d) Those in which heat operates 
to set free chemical affinities whereby the cell is caused to operate. 
(c) Thermo-chemical cells, in which a difference of potential is 
maintained by keeping one plate at a higher temperature than the 
other. 

Checking Instrument. An instrument used in cable telegraphy 
to verify despatches by printing dots and dashes on the siphon 
recorder strip. 

Chemic. A unit of current proposed by J. T. Sprague. It is 
that current which, flowing through a voltameter, liberates one 
grain of hydrogen in ten hours. It equals 1/5.68 ampere. 

Chronoscope, Electric. An instrument for indicating small 
intervals of time. In one form of chronoscope an electro-magnetic 
detent releases a pendulum which carries a light pointer swinging 
along a graduated arc. Another electro-magnetic detent, at the 



STANDARD ELECTRICAL DICTIONARY. 



591 



expiration of the interval to be measured, clamps the pointer to the 
arc. The graduation at which the pointer stops gives the time 
between the two electric signals. 

Circuit Breaker, Automatic Magnetic. A form of automatic 
switch which opens a circuit when the current in it attains too high 
a value. 




Fig. 357. Circuit Breaker. 

The switch, drawn open by a spring, is kept closed by a latch 
which is released by an electro-magnetic mechanism which is 
traversed by the current. 

Synonym — Magnetic Cut-out. 

Circuit Breaker, Vacuum. A circuit breaker in which the 
contacts points are enclosed in a vacuum. The object is to break 
an inductive circuit instantaneously and without spark in order to 
intensify the inductive effects. One of the contacts is attached to 
a vibrating or a rotating armature which is set in motion by a 
laminated core electro-magnet just outside of the vacuum tube 
containing the contacts. 

Coherer. An exceedingly sensitive means of detecting electric 
waves. In one form two metallic electrodes, one of which is a 
spring, are just lightly touching each other; a galvanometer and 
batter}^ in circuit with them indicate practically an open circuit. 
The instant, however, an electric wave sweeps across the electrodes 
they " cohere " and the galvanometer is deflected, showing a low 
resistance. Some force is required to separate the electrodes. 
(See Relay, Marconi's.) 

Coil, Damping. A small coil mounted on an adjustable stand 
and placed near a galvanometer so that, by sending occasional 
currents through the coil, the galvanometer may be quickly 
brought to zero. 



592 



STANDARD ELECTRICAL DICTIONARY. 



Coil, Compensating. An adjustable resistance connected as a 
shunt to the series field coils of a compound wound dynamo, so 
that the compounding may be varied if necessary. 

Coil, Tesla. A form of induction coil adapted to give high 
potentials and high frequencies. 

The primary coil, of but few turns, is connected to an influence 
machine or the secondary of a spark coil, a spark gap and condenser 
are placed in parallel across the connecting wires. 

The secondary coil, of finer wire is wound on a reel of rubber. 
No core is used. 

Both primary and secondary are immersed in a bath of paraffine 
oil out of which the conductors are led in glass or vulcanite tubes. 



Comparative Indicator. 

used 



A form of differential galvanometer 

on the Edison three-wire system to 

compare the potential of the mains at various 

feeding points with the potential maintained 

by the standard feeder. 

Condenser, Adjustable. A condenser 
whose capacity can be varied by connecting 
any required part of it to a circuit. 

Synonym — Sub-divided Condenser. 

Condenser, Multiple=Series. An adjust- 
able condenser whose sections may be con- 
nected in parallel or in series. 

Conductivity Bridge. An instrument for measuring low resist- 
ances such as copper rods, etc. 





Fig, 359. Conductivity Bridge. 

Conductor, Twin. A cable containing two separately insulated 
wires. It is used in single tube systems of iron armored interior 
conduit. 

Conduit, Flexible. A tube woven of and impregnated with 
insulating and waterproofing materials and used as an interior 
conduit, q.v. 



STANDARD ELECTRICAL DICTIONARY. 593 

Conduit, Interior. A system of tubing with suitable couplings, 
elbows, junction boxes, etc., intended to be installed in a building 
during construction, and to receive subsequently the conductors, 
cut-out blocks, etc. , for supplying current throughout the building. 
The tubes are supplied of plain insulating material ; or of steel, 
iron, or brass, lined with a suitable insulation. 

Conduit, Railway. A subway containing conductors for supply- 
ing current to an electric railway, and arranged so that the current 
mav be led from the conductors to the car motors. 




Fig. 360. Contact Maker. 

Contact Maker. A device for connecting an electrometer or 
other instrument to the terminals of an alternator or transformer 
under test for a small fraction of each revolution, and also at any 
desired position of the armature in its revolutions. The apparatus 
is used in obtaining the curve of E. M. F. generated by alternating 
current machines. 

Co=phasal Alternations. Alternations whose E. M. F.'s are 
similar and synchronous. When alternators are in step, their 
alternations are co-phasal. 

Core Pins. Small copper or brass pins which are set into the 
poles of an electro-magnet to prevent adherence of the armature 
by residual magnetism. A thin plate of copper is sometimes used 
for the same purpose. 

Core=Ratio of Cable. The ratio of the diameter of the insula- 
tion of a cable to the mean diameter of the strand. 

Coulomb, International. The legal unit of electric quantity 
defined by the International Congress at Chicago, in 1893. It is the 
quantity of electricity transferred by a current of one international 
ampere in one second. 



594 STANDARD ELECTRICAL DICTIONARY. 

Coupling, Electric. A device for properly connecting the 
signal or lighting wires of the successive cars in a railway train. 

Cross Arm. A bar fastened at right angles to the upper part of 
a pole for the purpose of supporting insulators and electric wires 
attached thereto. 

Cross=Over. A device used at a crossing of two electric trolley 
roads to enable the trolleys to pass the crossing without jumping or 
sparking. 

Cryptoscope. A form of nuoroscope, q.v., having a lens at the 
eye end to magnify the fluorescent image. 

Cups, Leadings In. A form of insulator used to protect and 
insulate wires entering a building. 

Current, Marking. A current intended to record a dot or a 
dash on the paper ribbon in the polarized receiver of Wheatstone's 
automatic telegraph. 

Current, Spacing. A current the opposite in direction and 
purpose to the Marking Current, q. v. 

Current Tap. An adapter fitting a lamp socket so that the lamp 
may be still in use while current is being supplied by a flexible cord 
to a portable lamp, motor, or other device. 

Curve Tracer, Ewing's. An instrument for giving the hys- 
teresis curve of a given sample of iron at any desired frequency of 
alternation of the magnetizing current. 

Cut=Out, Film. A device used with incandescent lamps run in 
series on constant current circuits to short circuit the lamp termi- 
nals at the moment of rupture of the filament. It consists of a film 
of paper placed between the spring short circuiting terminals. 

This film is an insulator at the P. D. of the lamp, but breaks 
down under the full line E. M. F. The resulting arc burns out the 
paper and completes the circuit. 

Cut«=Out, Fixture. A safety cut-out small enough to be readily 
concealed within the canopy of the fixture which it protects. 

Cylindrical Bridge. A form of the meter bridge which is ren- 
dered more compact by having the slide wire wrapped helically 
around a rotating cylinder of insulating material. 

Dart. A spool-shaped piece of wood about six inches long, with 
a leather washer on each end, arranged to make it fit air-tight into 
subway ducts. It is provided at one end with a ring to attach a 
cord to in the operation of pneumatic rodding, q. v. 

Dead-End. A termination of a pole line wire by anchoring the 
wire to an insulator. 



STANDARD ELECTRICAL DICTIONARY. 



595 



Dead=Man. A short, stout wooden bar on one end of which are 
two iron guards, U-shaped, with a short, sharp spike between thern. 
It is used to temporarily support a telegraph pole while it is being 
raised to a vertical position. 

Synonym — Butt-Prop. 

Deflagrator. A voltaic cell of low internal resistance. So 
named by its inventor. Prof. Hare, from its ability to volatilize 
metallic wires. 

Synonym — Calorimotor. 

Device, EIectro=Receptive. Any device which is operated by 
the passage of a current. They may be classed by the form of 
energy into which the electrical energy is translated ; as, in the 
electric motor and telephone motion is produced, in an electric 
lamp radiant energy is produced, in the charging of a storage cell 
chemical energy is rendered latent. 

Synonym — Translating Device. 

Dextrorsal. Right-handed. Applied to the winding of a coil. 




Fig. 361. Theater D: 

Dimmer, Theater, An arrangement to diminish the power of 
the lights in a theater and especially on the stage. Rheostats are 
used for controlling direct currents and choking coils, q. v., for 
alternating currents. In Fie:. 361, is shown a bank of sixteen dim- 
mers arranged so that any of them can be controlled simultaneously 
by a main lever so as to affect a number of different circuits at once. 



The science of the refraction of light. 

A phenomenon of impedance to 



Dioptrics. 

Discharge, Alternative. 

high frequency discharge. 

If a Ley den jar be discharged through a long copper wire bent 
into a rectangle but having the ends of the wire separated by, say, 
half an inch, the discharge will take place across the air gap rather 
than through the wire. 



59^ 



STANDARD ELECTRICAL DICTIONARY. 



Discharge, Tesla. A disruptive discharge of exceedingly high 
frequency. 

Distributing Board. A connection board to which electric 
mains are brought and from which branch mains are led. It carries 
safety fuses, and frequently plug or knife switches. 

The term is sometimes applied to a cross-connecting board, q. v. 

Distribution, Center of. (a.) Any point at which a feeder is 
connected to a system of mains. 

(b) A panel on which a main is connected, through cut-outs and 
switches, to a set of branches. 

Distribution, Electrical, Efficiency of. The ratio of the 
energy in the electro-receptive devices — lamps, motors, etc. — to the 
total energy in the circuit. 

Door Trip, Electric. A device that 
closes an alarm circuit for an instant 
during the opening of a door. It is used 
in offices and small stores to give notice 
of a person entering. It is arranged so as 
to give no alarm when the door is being 
closed. 

Synonym — Door Trigger. 

Drift of Needle. The variation of a 
galvanometer needle from the zero point 
at times when no current is passing 
through the instrument. It is most often 
due to variation in the torsion of the 
suspension, or to moving magnetic masses 
in the vicinity. A less frequent cause is 
a change in the magnetic condition of the 
needle, causing it to take up a new posi- 
tion under the influence of the earth's 
field and the controlling magnet. 

Dynamo, Heteropolar. A dynamo in 
which the armature conductors pass from 
being opposite to a north pole piece to being opposite a south pole 
piece, etc. Dynamos in common use are heteropolar. 

Dynamo, liomopolar. A dynamo in which the armature, 
which is a copper disc or cylinder without iron, moves continuously 
past poles of one kind only. The first homopolar dynamo was 
Faraday's disc, q. v. 

Synonym — " Non-polar " Dynamo. 

Dynamo, Multi=Circuit. A dynamo so constructed as to supply 
two or more independent circuits. 




Fig. 362. 
Electric Door Trip. 



STANDARD ELECTRICAL DICTIONARY. 597 

Dynamotor. A combined motor and dynamo whereby a current 
of any description, — continuous, alternating, high or low voltage, — 
may be transformed into any other form of current desired. The 
watts of intake are, of course, greater than the watts output. 

Dynamotors may be constructed of three principal types : — 
(a) A motor coupled to the shaft of a dynamo. (6) A motor whose 
armature has two windings, one carrying the motive current, the 
other delivering the secondary current, (c) A motor which has 
wires connected to certain of its commutator segments, and leading 
to a set of two or more collecting rings. 

Dynamotors are used wherever a different current is desired from 
what is available. 

Synonyms — Current Reorganizer — Motor Dynamo — Rotary 
Transformer. 

Edgewise System of Switch Board Construction. A system 
devised by Van Vleck whereby the control of a large electric station 
may be brought under the supervision of one person. In the 
system, all instruments stand out at right angles to the face of the 
switch board, and are all of a standard width. 

All the apparatus belonging to a given circuit is placed vertic- 
ally, — the rheostat, main switch, fuses, ammeter, voltmeter, etc., 
being set one above the other. 

As the width of such a set of instruments is within five inches, it 
is readily seen how a large number can be placed in a given space. 

The instruments are of special design having the divided scale 
at their edge. The rheostat switches have the handles at the edge, 
moving over an arc, as in a stage regulator. 

Efficiency, Torque. The ratio of the torque of the motor to 
the torque which it would give at the same power input if there 
were no internal losses in the motor. ^Steinmetz.) 

Efficiency, Torque, Apparent. The ratio of the torque of an 
alternating current induction motor to the torque which it would 
give at the same volt-ampere input if there were neither internal 
losses nor phase displacement in the motor. (Steinmetz.) 

Electrician. One versed in the principles and applications of 
electrical science. 

Elevator Signal, Electric. A device whereby a person on any 
floor of a building can, by pressing a button, cause a signal to 
operate in the first approaching elevator car which is moving in 
the direction he desires to go. 

Electrobat. A name proposed for an electrically propelled 
carriage. 



598 STANDARD ELECTRICAL DICTIONARY. 

Electrocution. Capital punishment inflicted by electric current 
from a dynamo of high electromotive force. (See Deaths Elec- 
trical. ) 

Synonyms — Electrothanatosis — Electrotisis — Electrozemia. 

Electrograph. An electrometer which record photographically 
the static condition of the atmosphere. 

Electrolabrum. A name proposed for a candelabrum fitted with 
incandescent electric lamps in the form of candles. 

Electro=magnet, Portative. An electro-magnet designed to 
exert a pull upon the armature when the armature is in contact 
with the poles. Such magnets are used on derricks, for lifting 
irregular masses of iron ; on machine tools, for chucking or hold- 
ing odd shapes to be operated on, etc. 

Electro = magnet, Tractive. An electro-magnet designed to 
exert a pull on its armature at some distance from the poles. Such 
magnets are used in bells, sounders, annunciators, telephone 
receivers, etc. 

Electrotherm. A variety of flexible electric heater for thera- 
peutic uses. It consists of a felt pad within which is an asbestos 
mat in which is woven a resistance wire. The heat radiated may 
be varied by a switch which is connected to different sections of 
the embedded wire. 

E. M. F. An abbreviation for electromotive force. 

The force that causes electricity to move along a conductor. 

Emissivity. The rate of radiation of energy from a body. It is 
an important factor in incandescent lamp making, as the amount 
of heat dissipated by a filament, that is, its rate of cooling, depends 
very much on the nature of its surface. 

End Connectors. Copper plates which are used to make the 
proper connections of the armature conductors in a bar armature, 
q. v. 

Engineer, Electrical. One who is versed in or who practices 
that branch of science which embraces the designing, making, 
installing and using of electrical devices and machines and the 
various appliances necessary to connect and operate them. 

Entrefer. The space between the face of a pole-piece and the 
iron of the armature of a dynamo. It is the same as the air gaps, q. v. 

Exchange, Automatic Telephone. A form of exchange con- 
taining multiple switches which are moved by electro-magnetic 



STANDARD ELECTRICAL DICTIONARY. 599 

mechanism operated by currents sent from the subscribers' instru- 
ments. Each subscriber may, therefore, by the operation of his 
calling mechanism, cause his instrument to be connected to that of 
any other subscriber he wishes. 

el*. The symbol for the unit of magneto-motive force, the 
gilbert, q. v. 

Factor, Impedance. The ratio of the impedance to the ohmic 
resistance of a conductor. It equals the secant of the angle of lag. 

Factor, Reactance. The ratio of the reactance to the ohmic 
resistance of a conductor. It equals the tangent of the angle of lag. 

Farad, International. The legal unit of electrostatic capacity 
defined by the International Congress at Chicago, in 1893. It is 
the capacity of a condenser charged to a potential of one inter- 
national volt by one international coulomb of electricity. 

The practical unit of capacity is the microfarad, which is one- 
millionth of the above. 

Feeder Clip. A form of clamp whereby a feeder wire may be 
readily connected to a trolley wire. 
Synonym — Feeder Clamp. 

Feeding, Anti=Parallel. A method of current supply to a pair 
of conductors having electro-receptive devices connected in 
multiple arc. It consists in running a feeder from the source to 
the opposite ends of the conductors, so that the current enters one 
of the conductors at one end, passes through the lamps, etc., in 
parallel, and flows in the same direction to the opposite extremity 
of the other conductor. 

Fibre, Vulcanized. An insulating substance composed of 
cellulose treated with a metallic chloride. It is supplied in white, 
red or black. The specific resistance of white vulcanized fibre in 
ohms per cubic centimeter is 14X10 12 . 

Filament, Squirted. A variety of incandescent lamp filament 
produced by ejecting a solution, for instance, of cotton wool in 
chloride of zinc, through a small hole into a vessel of alcohol, 
which causes it to set and harden. The thread thus produced is 
afterward carbonized. The process has the advantage of readily 
giving filaments of any desired diameter. 

Fixture, Combination. A fixture provided with both gas and 
electric lights. 

Flaming. A phenomenon of the voltaic arc. In arc lamps 
flaming may be due to bad feeding of the carbons, the arc growing 



600 STANDARD ELECTRICAL DICTIONARY. 

too long before the mechanism acts ; or to impurities in the carbon 
which vaporize and produce a conducting flame. 

Fluorescent Screen. A thin screen coated on one surface with 
a fluorescent substance, such as potassium platino-cyanide, or 
calcium tungstate. It may be arranged in a fluoroscope, q. v., 
or mounted in a vertical frame in front of a source of X-rays so 
as to be seen by an audience. 

Fluoroscope. A box of optically opaque material, open at one 
end and shaped there so as to fit the face snugly about the eyes, 
and having a fluorescent screen, q. v., at the other end. 

The function of the arrangement is to exclude all extraneous 
light from the eyes so that any fluorescence of the screen may be 
easily observed. 

Fountain, Electrically Illuminated. A fountain in which the 
jets, sprays, etc., are lit up by powerful beams of light thrown so as 
to envelop the jet. 

A chamber beneath the fountain contains projectors, one below 
each set of jets ; the light from these passes up through changeable 
color screens, through a plate glass in the floor of the basin, and 
upwards in the direction taken by the jets. 

Galvanometer, tielmholtz. A tangent galvanometer having 
its coils wound on two rings which are placed parallel to each 
other and at equal distances on opposite sides of the needle. The 
object is to form a more uniform magnetic field at the needle. A 
modification by Gaugain has the coils on conical spools, whose 
surfaces, if produced, would have a common apex in the needle. 

Galvanometer, Lecture. A galvanometer having a large, dis- 
tinct scale and prominent pointer so that its deflections may be 
clearly seen by an audience. 

Galvanometer, Oil Vessel. A galvanometer in which the 
vibrations of the magnetic system are retarded by a platinum plate 
attached to the suspended system and dipping into an oil vessel. 

Galvanometer Plug, Dead Beat. A tubular plug arranged to 
fit into the coil of a reflecting galvanometer, and carrying within 
it a fibre-suspended mirror with magnetic needles attached. 

The swing of the mirror is limited by two circular glass windows 
whose distance apart is adjustable ; the damping is effected by the 
air confined between these windows ; this space is sometimes filled 
with glycerine. 

Galvanometer, Speaking. A dead-beat reflecting galvano- 
meter adapted to receive signals from a submarine telegraphic 
cable. 



STANDARD ELECTRICAL DICTIONARY. 601 

Galvanometer, Tangent, Universal. A tangent galvanometer 
having its coils wound on two annular spools mounted on slides at 
opposite sides of the needle box. The coils are always placed 
equidistant from the needle. The sensibility of the instrument 
with any pair of coils may be adjusted by varying the distance of 
the coils from the needle. 

Gauge, Ampere. A simple form of ammeter for switch board 
use. 

Gauss. The practical unit of magnetic intensity, or flux-density. 
It is the flux-density produced by a flux of one weber, q. v., passing 
perpendicularly through an area of one square centimeter. Its 
dimensions are L M T" 2 (force) —7 L 2 M 5 T" 1 (strength of pole)= 
L* M* T 1 . 

Its symbol is 08. 

Gilbert. The practical unit of magneto-motive force. It is equal 

to or 0.7958 ampere-turn. 

4 it 

Its symbol is cF. 

Ground Indicator. An instrument used to show the presence 
of a ground on an electric lighting circuit. A voltmeter whose 
resistance is known may be used and the resistance of the ground 
calculated from its readings. 

Synonym — Ground Detector. 

Grothuss' Hypothesis. A hypothesis devised by Grothiiss to 
account for the electrolytic phenomena in a voltaic celL Its 
assumptions are as follows : 

(1) That before the electric circuit is closed the molecules of the 
electrolyte are arranged in an irregular or unpolarized condition, 
as represented at 1, Fig. 363. These molecules are shaded to indi- 
cate their polarity and composition, the light part representing 
H 2 and the dark part S0 4 . 

(2) When the circuit is closed and a current begins to pass, a 
polarization of the electrolyte, as shown at 2, ensues, whereby all 
the negative ends of the molecules of hydrogen sulphate, or 
sulphuric acid, are turned towards the positive or zinc plate B, and 
all the positive ends towards the negative plate. This will turn the 
S0 4 ends towards the zinc, and the H 2 ends towards the copper. 

(3) A decomposition of the polarized chain, whereby the S0 4 
unites with the zinc and the H., liberated reunites with the S0 4 of 
the molecule next to it in the chain, and its liberated H 3 with the 
one next to it, and so on until the last liberated H 3 in the chain is 



602 



STANDARD ELECTRICAL DICTIONARY. 



A 



/ 



~.2T_ 



\ 







:*i&~- 



Fig. 363. Grothuss' Hypothesis. 

given off at the surface of the copper or negative plate. This 
leaves the chain of molecules as shown at 3. 

(4) A semi-rotation of the molecules 
« A o of the chain, by polarization as in (2), 

until they assume the position the 
same as shown at 2. 

eK. 




Fig. 364 
Fleming's Hand Rule. 



The symbol for magnetizing 
force. Its denning equation is: — 
qrr_4 it N I 
~ h~ 
in which N = the number of windings ; 
L, = the length of the magnetizing 
solenoid ; and I = the intensity of the 
current in amperes. Its dimensions 
are the same as the gauss, q. v. 

Hand Rule, Fleming's. Dr. Flem- 
ing's useful rule for remembering the 
relation between motion, magnetism 
and induced E. M. F. is as follows : 
If the right hand be held, as shown 
in Fig. 364 with the extended /ore- 
finger pointing in the direction of the 
the direction of the wotion, then the 



/lux, and the thm/zb in 

E. M. F. induced will be directed as the middle finger points. 

The application of the rule to motors is the same, except that the 
left hand is to be used. Holding the left fingers similarly, the 



STANDARD ELECTRICAL DICTIONARY. 603 

rule reads : The forefinger represents the direction of the /"lux, 
the mzddle finger represents the direction of the current i, and 
the thu;/zb points out the direction of the motion. (Houston and 
Kennelly.) 

Horus, Bone of. An ancient Egyptian name for the lodestone. 

Human Relay Working. In telegraphy, and especially in sub- 
marine telegraphy, the translation of a message from one circuit 
directly to another by an operator who transmits to the second cir- 
cuit, direct from signals received on the first, without writing down 
or transcribing the message. 

Synonym — Manual Translation. 

Humming of Transformer. A noise produced by an alternating 
current transformer. It is due to the mutual repulsion of the iron 
sheets of the core, the mutual attraction of the turns in the coils, 
and to the Page effect, q. v.. in the core. It is diminished by 
tightly clamping the core sheets and binding the coils. 

Igniter, Electric. A device used for firing the explosive mix- 
ture in a gas or gasoline engine. It consists of a pair of contacts 
between which a spark is_drawn by a cam at the proper instant. 

Synonym — Exploder. 

Illuminated Dial Instrument. Any engine-room or switch- 
board instrument having a dial of porcelain, or ground glass with 
opaque pointer, graduation and figures ; and lit up by an incan- 
descent lamp behind the dial. 

Illumination , Cosine Law of. The intensity of the illumination 
received by any element of a surface is directly proportional to the 
cosine of the angle between its normal, and the direction of the 
incident rays. 

Induction, Electro=dynamic. The production of E. M. F. 
in a conductor, when in a field of magnetic force, by moving the 
conductor or the lines of force so that, practically, the conductor 
cuts the lines of force. 

There are four modes of electro-dynamic induction : — 

(a) Self induction or inductance, of a conductor on itself. 

(b) Mutual induction, of a current on a near circuit. 

(c) Electro-magnetic induction, of a conductor moving in a 

magnetic field. 

(d) Magneto-electric induction, of a field moving across a 

conductor. 

Induction Plate. The disc, in an absolute electrometer, q. v., 
which is carried by an insulating stem and moved by a micrometer 
screw. 



bo4 



STANDARD ELECTRICAL DICTIONARY. 



Insulator, Awning. A curved tube of insulating material for 
the protection of wires passing near or around the iron frame of an 
awning. 





Fig. 365. Battery Insulator. 

Insulator, Battery. An insulator made to be placed under the 
individual cells of a primary or storage 
battery to prevent leakage of current, 
which may take place either through 
the material of the jar or through damp- 
ness of its sides. The form shown in 
Fig. 365, has a layer of heavy oil in the 
lower cup. 

Insulator, Floor. A tube of insu- 
lating material to give protection and 
additional insulation to a conductor pass- 
ing through a floor. 

Insulator, Section. An insulator 
for maintaining the electrical separation 
of adjacent sections (see Trolley Section) 
of a trolley wire while permitting the 
trolley to pass easily from one section to 
Fig. 366. the next. 

Floor Insulator. Insulator, Strain. A form of insula- 

tor to be placed in the guy wires of a trolley line. It is adapted 
to withstand severe tensions. 





Fig. 367. Strain Insulator. 

Insulator, Transposition. A two-grooved insulator used in 
transposing telephone line wires. In a metallic (two wire) cir- 
cuit the two lines are cut at a pole, the two ends of one wire are 



STANDARD ELECTRICAL DICTIONARY. 605 

dead-ended on one insulator, and the two other ends are similarly 
fastened ; then two short wires, called " transposition wires," 
q. v., are used to make the cross connections. (See Transposing.) 

Insulating Cements. Compounds of various gums possessing 
the property of binding substances firmly together, and at the same 
time maintaining electric insulation between them. Common 
sealing wax and jewelers' cement are good. The following is 
recommended : Shellac, 5 parts ; resin, 2 parts ; Venice turpentine, 
1 part ; yellow ochre, 3 parts. 

Insulating Table. A stand supported by a carefully insulated 
rod. It is used to insulate objects in statical experiments and 
tests. 

Insulation, Electric. The dielectric or non-conducting mate- 
rials which are used to prevent the leakage of electricity. Some- 
times it is made to surround a wire, as in magnet wires, cables, 
etc. Sometimes the insulation supports the conductor at intervals, 
as a bus bar on porcelain blocks, or a telegraph w T ire on glass knobs. 
In these instances the air is for the most part the insulation. 

Intake. The amount of energy absorbed by a machine. The 
output divided by the intake gives the efficiency. 

Joint, Insulating. A coupling for attach- 
ing an electrolier or combination fixture to a 
gas outlet while insulating it therefrom. 

Joint, Paste. In an incandescent electric 
lamp a joint between the filament and the 
leading-in w T ires, made by applying a carbon 
paste to the parts and then hardening the 
joint by heat. 

Joint, Sleeve. A form of splice for single 

Fig. 368. wires in which the two ends are run from 

Insulating Joint. opposite directions into a double cylinder of 

thin copper. The ends of the wire may be 

brought through and wound around the adjacent wire, or the 

whole sleeve may be twisted by suitable tools, and thus clamp the 

wires securely. Apertures are usually provided in the sleeve so 

that solder may be run in. 

Jumper. A short length of wire used to connect around a break 
in a circuit. It must be of equal current capacity to the line it 
connects. (See App. Anti-Hum.) 

Synonym — Bridle. 

Key, Mouth. A special form of telephonic transmitter, having 
a contact so arranged with reference to the vibrating diaphragm as 






606 STANDARD ELECTRICAL DICTIONARY. 

to break a circuit at the sound of the voice. It is used in physio- 
logical reaction -time experiments. 

Key, Multiple. A key so constructed that it can be adjusted to 
close or open more than one circuit at the same instant or suc- 
cessively. 

Key, Pistol. An attachment to the muzzle of a pistol so that a 
circuit is broken when the pistol is fired. (See App. Key, Runner's.) 

Key, Reaction. A key adapted to be readily held in the hand, 
and arranged with adjustable contacts so as to make or break an 
electric circuit by a slight movement of the fingers. 

Key, Runner's. A key which is arranged to break an electric 
circuit when an athlete starts to run. It is used in connection 
with a pistol key and chronograph in physiological reaction-time 
experiments. 

Key, Signaling. A key for sending messages by a submarine 
cable. 




Fig. 369. Strap Key. 

Key, Strap. A key in which the movable contact is an elastic 
strip, at one end fastened to the base of wood or rubber, and at 
the other bearing a button or knob. 

Key, Successive Contact. A key arranged to close two 
separate circuits successively. (See Key, Bridge.) 

Key, Touch. A flexible pointer or rod mounted in a handle 
and provided with contacts so as to break an electric circuit when 
a person or object is touched by the pointer. 

Konstantan. An alloy used in making resistance coils. It has 
a zero temperature co-efficient, but gives a small thermal E. M. F. 
with copper. 

Lag, Angle of. An angle whose tangent equals ratio of the 
inductive to the ohmic resistance. 

Lamp Bulb. The glass globe containing the filament of an 
incandescent electric lamp. Its function is to maintain the high 
vacuum upon which the life of the filament so greatly depends. 



STANDARD ELECTRICAL DICTIONARY. 607 

Lamp Bulbs, Blackening of. A darkening of the bulb of an 
incandescent lamp due to particles of carbon thrown off from the 
filament. This action reduces the light emitted, in three ways : 

(a) By a coating of opaque carbon on the glass. (b) By alter- 
ing the surface of the filament so that it radiates more heat and is 
consequently cooler. (c) By increasing the resistance of the 
filament so that less current passes. 

Lamp, Efficiency of. This is ordinarily given as the number 
of watts required to produce one candle-power. Although in com 
mon use this rating may be misleading, as it is obvious that the 
greater the watts per candle the less is the efficiency. 

The real efficiency is the reciprocal of the above, or, the candles 
per watt. 

Lamp, Enclosed Arc. A form of lamp in which the arc is en- 
closed within a small bulb with apertures through which the 
carbons pass snugly. The fresh air is thus excluded and the life 
of the carbons is increased about twelve times. 

Lamp Guard. A wire frame to protect an incandescent electric 
lamp from accidental breakage. 

Lamp=Stand and Scale. An arrangement for observing the 
indications of a mirror galvanometer. (See Galvanometer, Reflect- 
ing: 

Lamp* Theater. A focusing arc lamp placed 
in a lantern on an adjustable, portable stand 
and provided with lenses, colored screens, etc., 
for illuminating an actor or a scene. 

Legging=Key Board. A connection board 
in a telephone exchange employed for the pur- 
pose of connecting an operator's instrument into 
direct circuit with two or more subscribers. 

Light Indicator. A form of annunciator in 
circuit with a battery and thermostat. It is 
used to indicate whether the lamp in a railway 
signal lantern is burning or not. 

Lighting, Vacuum Tube. Illumination by 
high potential alternating discharges through 
vacuum tubes. The advantage of this mode of 
lighting is that the light is produced without 
the usually accompanying heat. It is a cold 
glow illumination. The vacuum tubes used are 
six or eight feet long and placed in the cornice 
Fig. 370. of a room. They may be given various decora- 

Thkater Lamp. tive forms. 




6o8 



STANDARD ELECTRICAL DICTIONARY. 



Lightning Arrester, Air Expansion. An arrester in which 
the discharge and ensuing arc takes place between a fixed and a 
hinged carbon electrode in a small marble box. The sudden air 
expansion forces the hinged electrode out of the box, breaking 
thereby the arc, and into a similar adjoining box where it rests 
opposite another fixed electrode ready for another discharge which 
will throw it back into the first box. 

Lightning Arrester, High Resistance. An arrester in which 
the discharge jumps across several air gaps in series. The number 
of air gaps is so chosen that the E. M. F. is unable to maintain an 
arc across them. 

Lightning Arrester, Non=Arcing. A lightning arrester in 
which the property of non-arcing metals, q. v., is availed of. 

A slate base carries seven parallel cylinders of non-arcing metal 
at a distance from each other of about g^-inch. The exterior cylin- 
ders are connected to line, and the middle one 
is grounded. The flash thus crosses three 
air-gaps. 

Lightning Arrester, Swinging Ball. An 

arrester in which the discharge passes between 
a suspended metallic ball and an electrode im- 
mediately below. 

The sudden air expansion due to the ensuing 
arc causes a violent swing of the ball away from 
the lower electrode, thus breaking the arc. 

Line, Artificial. A set of resistance coils 
and condensers so connected as to form the 
equivalent in resistance and capacity of an ser- 
ial or subterrene line. 

Fig. 37 r. Line, Wind and Water. A place on tele- 

S winging Ball graph poles, close to the ground, at which 
Lightning Arrester, decay generally begins to take place. 

Load Diagram. A curve, usually plotted on cross-section paper, 
in which the X axis is divided into time intervals, hours or days, 








A, — .-■ — - 


S. - - 




_7 v 


(II 


1 A 


__ — ^ 


-"^ 


" s^ 


\J 


s c ^ V- 








£ , 




n T : : : 





Fig. 372. Load Diagram. 



STANDARD ELECTRICAL DICTIONARY. 609 

and on the corresponding ordiuates is laid off the load of the gen- 
erating plant at these particular times. It is shown by the curve 
C P D, in Fig. 372. 

Load Factor. The ratio of the actual output of any given plant 
to its output if it were worked continuously at full load for the 
same period. In the load diagram, Fig. 372, it is the ratio of the 
area C P D X O, to the rectangle A B X O. 

Load, Peak of. The greatest load which a station is called upon 
to supply in any given period. It is shown at P, in Fig. 372. 

Loss, C 2 R. An expression for the loss of energy of a current in 
its passage through a conductor. The watts lost in heating a con- 
ductor are equal to the product of the current by the E. M. F., at 
its terminals, or W=CxE. But E=CxR ; substituting this value 
gives W=C' 2 XR. . - 

The equation is oftener used in this form because the resistance 
is more easily found (from tables) than the E. M. F. 

Luminescence. A power possessed by certain substances of 
emitting light after having been exposed for a time to luminous 
radiations. 

Although commonly called phosphorescence, it is quite a differ- 
ent phenomenon. 

jn. The symbol for magnetic permeability. 

Magnetic Circuit, Air=. That part of a magnetic flux path 
which lies entirely in the air. 

Magnetic Circuit, Closed=. A magnetic circuit which flows 
entirely in iron or other paramagnetic substance. 

Magnetic Induction, Lines of. 

Lines which show the direction and 
quantity of the lines of force in a 
magnetic field. 

Magnetic Spectrum. The figures 
produced by iron filings upon glass 
or paper held near magnetic poles. 

(See Magnetic Field of Force — 
Magnetic Curves.) 

Synonyms — Magnetic Phantom. 
Magnetic Figures. 

Fig. 373. Magnetite. Magnetic oxide of 

Magnetic Spectrum. iron . a black oxide of iron (Fe 3 4 

or FeO.Fe 2 3 ) which is strongly attracted by a magnet. 




610 STANDARD ELECTRICAL DICTIONARY. 

Metal, Non=Arcing. It was discovered by Wurtz that certain 
metals of the cadmium group would not sustain an arc between 
electrodes formed of them. It is probably because the spark, on 
crossing between the electrodes, volatilizes and oxides some of the 
metal and extinguishes itself by interposing a non-conducting 
vapor between the surfaces. 

This peculiar property has been utilized in the construction of 
lightning arresters. 

Meteorograph, Electric. An electrical apparatus for auto- 
matically recording various meteorological data, such as tempera- 
ture, height of barometer, direction and velocity of the wind, 
rainfall, insolation, etc. 

Meter, Telephonic. A clock which is allowed to run by the 
removal of the receiver from the hook. Replacing the receiver 
stops the clock, thus showing the time during which the instru- 
ment was in use. 

Metronome, Registering. A clockwork time-marking instru- 
ment arranged to close, at any desired interval, the electric circuit 
of a chronograph. 

Micanite. An insulating material made by cementing laminae 
of pure mica together with shellac or other suitable adhesive. Its 
toughness can be increased by preparing it with a backing of paper 
or cloth. It is largely used in armatures. 
Its specific resistance at 30° C. (86° F.) is : 

Micanite, 2490 X io 12 ohms. 

Micanite Paper, - 1240X10 12 " 

Micanite Cloth, - - - 310X10 1 ' 2 " 

Mil- Ammeter. An ammeter indicating thousandths of an 
ampere. 

Synonyms — Milliammeter — Milli-amperemeter. 

Mitis Metal. Wrought iron containing aluminum. 

M. M. F. An abbreviation for magneto-motive force. 

Motor, Constant-Current. A motor designed to be operated 
by a direct current of unvarying amperage. It is usually series 
wound .and provided with a governor which varies the field 
magnetism and so controls the speed. It is used on series systems 
of electrical distribution. 

Motor, Constant- Potential. A motor designed to be operated 
by a direct current of constant E. M. F. It is usually a shunt- wound 
motor. It is used on multiple arc systems of electrical distribution. 

Motor, Pilot. A small motor arranged to actuate the controller 
of a larger motor. By this means but small wires are necessary to 



STANDARD ELECTRICAL DICTIONARY. 611 

be run to the points of control, and at these points but a small con- 
troller is used. Pilot motors are used by F. J. Sprague in his 
electric elevators and the multiple-unit traction system. 

Multiplier for Voltmeter. (See Red net eur for Voltmeter.) 

Municipal System. A system devised by Edison in which 
incandescent lamps are connected in series to a dynamo of iooo 
volts E. M. F. It is intended for public lighting in towns and 
villages where the circuits extend over considerable area. 

v. The symbol for reluctivity. 

Oersted. The unit of magnetic reluctance. It is the reluctance 
offered by a centimeter cube of air-pump vacuum between opposed 
surfaces. (Houston and Kennelly.) Its dimensions are LT" 1 
(velocity) X L (length) -f- L 2 (surface) = T" 1 . 

Its symbol is cH. 

Ohm, International. The legal unit of resistance defined by 
the International Congress at Chicago in 1893. It is based upon 
the ohm equal to io 9 units of resistance of the C. G. S. system of 
electro-magnetic units, and is represented by the resistance offered 
to an unvarying electric current by a column of mercury at the 
temperature of melting ice 14.4521 grammes in mass, of a constant 
cross-sectional area, and of the length of 106.3 centimeters. 

Oil Bath. A tank containing oil in which standard resistance 
coils may be immersed in order that they may have an equal and 
readily determinable temperature. 

Oscillator, Hertz's. An apparatus devised by Hertz for pro- 
ducing electric waves. It consists of two insulated metal plates to 
each of which is attached a metal rod terminating in a knob. The 
two rods are connected to an induction coil and the knobs ap- 
proached until the disruptive discharge passes. The waves radiate 
from the plates into the surrounding ether. (See Resonance, 
Electric. ) 

Synonym — Hertz's Radiator. 

Ozokerite. A mineral substance which, by distillation, yields a 
material closely resembling paraffine, and a pitchy residue which 
is used to saturate the cotton covering of wires. Its specific 
inductive capacity is 2.13 (Hopkinson.) 

<P. The symbol for the unit of magnetic flux, the weber, q. v. 

Paint, Heat Indicating. A paint which changes color from 
vermilion to dark brown when its temperature is changed from 
ioo° F. to 150 F. It is useful for painting shaft and engine bearings, 
armatures, etc. It retains its properties for an indefinite number 




6i? STANDARD ELECTRICAL DICTIONARY. 

of heatings. Its composition is said to be :— five parts of red mer- 
curic oxide and one part vermilion mixed to a paint with oil and 
turpentine. 

Panel Board. A switch board used at a center 
of distribution. It carries safety fuses and knife 
or snap switches for the protection and control 
of the branch circuits. In Fig. 374 is shown a 
panel board arranged to carry fuses only. 

Paper Winder, Automatic. A clockwork 
device for reeling up the paper ribbon as fast as 
delivered from a register, recorder or ticker. 

Pen Carriage. In an electric chronograph, 
FlG> the carriage upon which is mounted one or 

Panel Board. more recording pens with their actuating mag- 
nets. (See Chronograph, Electric.) 

Permittance. A word proposed for dielectric capacity, q. v. 

Phase Detector. An instrument to indicate when the currents 
of two alternators are co-phasal, q. v. It is used when connecting 
alternators in parallel. 

Phonogram, (a) A record produced by a phonograph. 
(b) A dispatch transmitted by telephone. 

Phonoplex Telegraphy. A system of telegraphy in which in- 
duction currents from a suitable coil, superposed on the ordinary 
Morse currents, operate a form of telephone receiver. The system 
is used on railway lines to convey through messages between 
terminal stations on a wire also used for way traffic. 

Photo=Chronograph, Polarizing. A chronograph in which 
the record is made on a revolving photographic plate by a beam 
of polarized light. It contains two Nicol prisms which are adjusted 
so as to extinguish a beam of light. Between the prisms is a power- 
ful solenoid in which is a tube with plate glass ends and contain- 
ing bisulphide of carbon. Whenever a current passes through 
the solenoid, the plane of polarization is rotated in the carbon 
bisulphide and light is allowed to pass through to the photographic 
plate. Comparison of this impression with a tuning fork record 
on the same plate give the duration of the recording current. (See 
Magnetic Rotary Polarization.) 

Photo=Fluoroscopy. A method of taking radiographs by 
photographing with a regular camera the image on a fluorescent 
screen. It is on the principle that a prolonged photographic 
exposure will reveal more than is visible to the unassisted eye. 



STANDARD ELECTRICAL DICTIONARY. 



613 



Photometer, Flicker. An instrument in which the light from 
the brighter source is diminished in intensity by passage through 
apertures in a rapidly revolving disc. The amount of light passing 
is independent of the speed of the disc, but may be varied by 
closing gradually the apertures by a second perforated disc. Suit- 
able means are provided for doing this during rotation of the 
discs. 

Synonym — Napoli's Photometer. 

Pin. A peg of wood or metal to be fixed into a cross arm and 
support an insulator. 

Pitch of an Alternator. The distance from the center of a 
north pole-piece to the center of the adjacent south pole-piece. 

Plate Stove, Electric. A form of electric heater consisting of 
a round or square iron plate having resistances applied to its 
under side and suitably protected. The plate is used like an 
ordinary range top, to place kettles, etc., upon. 

Plug, Attaching. A plug with contacts for connecting a 
flexible conductor into a socket or receptacle. 

Pole, Center. A pole placed between 
the tracks of an electric trolley road, and 
provided with bracket arms to carry a trolley 
wire over each track. They are made to 
carry also feed wires, and sometimes arc or 
incandescent lamps to illuminate the road- 
way. 

Pole, Composite Anchor. A wooden 
pole, stiffened at the top with iron lattice- 
work so as to transmit the pull on the cross- 
arms to the guys without distorting the pole 
top. 

Pole Indicator, (a.) An instrument for 
determining the positive pole of an electric 
source. It may be a high-resistance pocket 
galvanometer, or a small electrolytic cell 
containing a metallic salt which will change 
in color at one of the poles. 

(b.) A compass used to determine the polarity of a magnet or 
the direction of a current. 

Pole Top. (a.) The upper portion of a pole with its cross-arms, 
braces, etc. 

(b.) A casting to surmount a trolley line pole and support feed- 
wire insulators and guard and trolley suspension wires. 





614 STANDARD ELECTRICAL DICTIONARY. 

Prefixes of Scientific Units. A series of prefixes, of Greek 
derivation, used to indicate multiples and sub-rnultiples of 
electrical and other units, as follows : 

MUI/f IPI.ES. 

deka 10 ten 10 

hecto ioo one hundred io 2 

kilo 1,000 one thousand io 3 

mega 1,000,000 one million io 6 

bega 1,000,000,000 one billion io 9 

trega 1,000,000,000,000 one trillion io 12 ■ 

quega 1,000,000,000,000,000 one quadrillion io 15 

SUB-MUI/TIPI,KS. 

deci 0.1 one tenth 10 * 

centi 0.01 one hundredth 10 2 

milli 0.001 one thousandth 10 3 

. micro 0.000001 one millionth 10 6 

bicro 0.000000001 one billionth 10 9 

tricro o. 00000000000 1 one trillionth io 12 

These are combined with the names of the units, as, bicrohm, 
milliampere, kilovolt, etc. Sometimes a consonant is inserted 
for euphony, as megalerg for megerg. The higher prefixes were 
introduced by Houston and Kennelly. 

Pressure Indicator. A form of voltmeter whose pointer is at 
zero when the conductors to which it is connected are at a required 
potential. A movement of the pointer to either side of zero 
indicates a potential greater or less than that desired. 

PulUOver. An insulator designed to retain a trolley wire in its 
proper place along a curve. 

Synonyms — Pull -off Insulator — Curve Bracket. 

Puncturing of Insulation. An expression denoting the 
piercing of a dielectric by a high potential disruptive discharge. 
Where this is likely to happen oil is often used as an insulation, as 
it forms a dielectric which is self-healing after a discharge. 

Push=Button, Indicating. A push-button containing a small 
electro-magnet with armature. The magnet coil is in series with 
the circuit, so that when the button is pressed the noise produced 
by the armature being attracted indicates that the current is in 
action. 

Synonym — Sounder Push. 

Quadmeter. A secohmmeter, q. v. 

eH. The symbol for the unit of reluctance, the oersted, q. v. 



STANDARD ELECTRICAL DICTIONARY. 615 

Radiator, (a) A form of electric heater for warming a room. 

(See Heater, Electric.) 

(b) An apparatus for producing electric waves. (See App. 
Oscillator y Hertz's.) 

(c) In a Crookes' tube, the anticathode from which the X-rays 
emanate. (See App. Rays, Cathodic.) 

Radiograph. A photograph taken by means of the X-rays. As 
the rays cannot be sensibly refracted no lens is used, the object 
being simply held between the source of the rays and a photo- 
graphic plate. The result is necessarily a shadow picture. 

Synonym — Skiagraph. 

Radiography. The art of making photographs by the use of the 
the X-rays. 

Radio=micrometer. A thermo-galvanometer which is sensitive 
to exceedingly minute quantities of radiant energy. As arranged 
by C. V. Boys, it consists of a small thermo-electric couple attached 
to a wire loop of small resistance. The couple and loop is sus- 
pended in the field of a D' Arson val galvanometer so that the loop 
takes the place of the usual coil. It is said to be sensitive to the 
radiations reaching the thermal junction from a candle two miles 
distant. 

Rake. The inclination given to a pole opposite in direction to 
the strain it is intended to bear. 

Rays, Becquerel. Invisible light rays of an extremely ultra- 
violet character ; i. e. , transverse vibrations in the ether of 
extremely short period and wave-length. They are emitted by 
fluorescent substances after exposure to light. They possess in 
some degree the properties of the X-rays. 

Rays, Cathodic. The radiant matter projected from the cathode 
of an excited Crookes' tube. 

The principal properties of the cathodic rays are as follows : — 

(a) That they leave the cathode in straight lines independent 
of the position of the anode. 

(b) That they exhibit themselves only in very high vacua. 

(c) That they produce a luminescence of the ratified gases 
and a fluorescence or phosphorescence of the wall of the 
tube or bulb, or of certain substances contained within the 
tube. 

(d) That the X-rays emanate from whatever within the 
tube is struck by the rays. 



616 STANDARD ELECTRICAL DICTIONARY. 

(e) That they are deflected from their straight course by a 

magnet exactly as if they were an electric current moving 

along a conductor. 
{/) That particles of material from the electrodes are 

carried along the line of movement, thus often coating the 

walls of the tube with these particles. 
(g) That they may be focused to a point or concentrated by 

giving the cathode itself the form of a concave mirror, or 

be otherwise distributed by changing the form of the 

cathode. (Morton and Hammer.) 

Rays, X. A peculiar form of radiation discovered and named 
by Rontgen, the precise nature of which is not yet known. The 
effects of the rays are as follows : — 

{a) Passing more or less readily through various substances, 
(lead glass is quite opaque, aluminum transparent.) 

(b) Producing fluorescence in certain bodies. 

(c) Producing an actinic effect on photographic plates. 

(d) Discharging an insulated, charged conductor. 

(e) Producing severe dermatitis and other peculiar and 
painful troubles on the skin when exposed too long to the 
rays. 

They are usually produced by a Crookes' tube, q. v., of suitable 
construction. 

Synonym — Rontgen Rays. 

Reactance. The component of the impressed E. M. F., at 
right angles to the current, divided by the current. 
It is expressed in ohms. 

^^Tiinni&fc Receptacle. An incandescent lamp socket 

HEir J designed to be fastened to a flat surface. 

:> Synonym — Wall socket. 

i li||B| Receptacle, Candelabra. A miniature lamp 
^jBj II receptacle designed to be concealed within a porce- 
;; I^^J lain tube representing a candle. 

I &)>y ' Rectifier, Alternating Current. An apparatus 

jP_U for obtaining a pulsating direct current from an 

! ! .! ' iinnilinnnillliilla^ alternating current. It consists of a synchronous 

§§§§§ alternating current motor driving a commutator 

|§Si§ which connects directly to line all current waves of 

^i^^ one direction, and reverses the connection of all 

Fig. 376. waves of opposite direction. It is used to operate 

.»«-. , ™, arc lamps and electrolytic baths. 

ANDELABRA £. ^ S , . 

eceptacle. (See Current, Rectified.) 



STANDARD ELECTRICAL DICTIONARY. 617 

Regulating Socket. A lamp socket containing a resistance, 




Fig. 377. Regulating Sockets. 

or a choking coil, the action of which may be controlled by 
a key or knob, so that the brilliancy of the lamp is varied. 

Relay, Double Balanced. A combination of two relays on one 
base, with their armatures so adjusted that either a very slight 




Fig. 378. Double Balanced Relay. 

increase or decrease in the line current will close the local circuit. 
It is used in burglar alarm systems. 

Relay, Marconi's. An instrument for receiving messages sent 
bv a system of high-frequency electric waves. It consists of a 
small glass tube 4 cm. long, into which two silver electrodes are 
sealed. 



618 STANDARD ELECTRICAL DICTIONARY. 

These electrodes are about yi mm. apart, a thin space intervening 
which is filled by a mixture of fine nickel and silver filings, mixed 
with a trace of mercury. The tube is exhausted to a 4 mm. vacuum. 
It forms part of a circuit containing a cell and a sensitive relay. 

In its normal condition the metallic powder is virtually an 
insulator, but when electric waves fall upon it the particles cohere, 
the resistance drops to, perhaps, 5 ohms, and the signal is received. 
The powder is caused to "decohere" by a vibrating hammer 
which strikes the tube. (See Resonance, Electric. In App. 
Coherer — Telegraphy, Wireless. ) 

Reluctivity, The reciprocal of permeability, q. v. Its symbol 
is v. 
Synonym — Reluctancy. 

Reluctivity, Metallic. The reluctivity of a metal alone, in- 
dependent of the reluctivity of the ether which pervades it. 

Resistance Coils, Aging of. A slight increase and subsequent 
decrease in the resistance of German silver coils which takes place 
for about three days after the winding of the coils. Coils may be 
artificially aged by heating them to a temperature of 140 C. (284 F.) 
for five hours in an air bath. 

Resistivity. The resistance of a cubic centimeter of a body, 
measured between opposite faces. 
Synonym — Specific Resistance. 

Resonator, Sounder. A small box, open only at one end, and 
containing a sounder. It is placed on an adjustable stand near the 
operator, so that he alone may hear the signals, and that they may 
be distinct from other sounds. 

Retarding Disc. A disc used in Thomson's electric meter for 
retarding the revolutions of the motor shaft so that the number of 
revolutions is directly proportional to the energy to be measured. 
The disc is of copper, and rotates between the poles of permanent 
magnets, the currents thereby induced in the disc react on the 
magnets and retard the disc. 

Rheostat, Continuous. A rheostat adapted to carry continu- 
ously any current up to a certain limit without change of resistance 
by heating. It is used in measuring current by the fall of potential 
method. 

Rheostat, Enamel. A form of rheostat for dissipating electrical 
energy in which the resistance, in the form of wires or ribbons, is 
held securely upon, but insulated from, a ribbed metal plate which 
acts to radiate the heat produced. 



STANDARD ELECTRICAL DICTIONARY. 619 

Riser. In the wiring of a building for incandescent lighting a 
riser is a conductor which is run vertically from floor to floor. 
Synonym — Vertical Main. 

Rodding a Conduit. A process preliminary to drawing a cable 
into a subway conduit. It consists in thrusting into the conduit a 
series of rods, connected by a suitable coupling. This is continued 
until the end of the conduit is reached, when a rope is fastened to 
the last rod and drawn through by the rods, which are uncoupled as 
they emerge. The cable is then hauled through by the rope. 

Rodding, Pneumatic. A method of introducing a rope or wire 
into a subway conduit. It consists in having a light wooden 
cylinder to which a cord is attached. This cylinder, or dart, as it 
is called, is placed in one end of a conduit ; at the other end a 
suction air pump is applied, and by a few strokes draws the dart 
and cord through. (See App. Rodding a Conduit.) 

Rosette, Ceiling. A block 
of insulating material fastened 
to the ceiling for suspending a 
pendant cord, and containing 
fuses and terminals for connect- 
ing the cord to electric mains. 

Synonym— Ceiling block. 

Rotator, Geissler Tube. A 

pivoted holder enabling a 
Geissler tube to be revolved 
Fig. 379. Ceiling Rosette. while maintaining its connec- 

tions with an induction coil or 
other source. It is usually furnished with a small motor 
which is operated from the same battery which works the induc- 
tion coil. 

Rotor. The revolving mass carrying the short-circuited con- 
ductors in a rotatory field induction motor. 

Sealing=in. A process in the manufacture of incandescent 
electric lamps. It consists in passing the filament with its mount 
in through the neck of the bulb and then fusing the bulb neck 
hermetically around the mount. 

Search Light, Electric. An apparatus for producing a pow- 
erful beam of light and projecting it in any desired direction. It 
consists of a focusing arc lamp provided with large carbons so as 
to use a heavy current ; the lamp is placed so as to throw the 
greater part of the light on to a lens or, more usually, a special 
reflector which turns the rays into parallelism. The lamp and 




'620 



STANDARD ELECTRICAL DICTIONARY. 



reflector are placed in a suitable lantern and mounted on 
trunnions, through which the conductors are brought. 

Sometimes the directing of the beam of light is done by two 
reversible motors in the pedestal, which are controlled by rheostats 
at a distant point. 

Synonym — Proj ector . 

Secohmmeter. An instrument for measuring the co-efficient 
of self-induction and the mutual induction of conductors. 

Section Box. A box containing the switches and fuses for the 
control and protection of a section of electric street railway con- 
ductor. 

Shoe, Electric. A shoe bearing contacts so* as to make an 
electric circuit when the foot is raised, and to break the circuit 
while the foot is on the ground. It is used in physiological experi- 
ments on walking, running, etc. 





/' x 



"000 1 



=0 



Fig. 380. Compensated Shunt Box. 

Shunt Box, Compensated. A galvanometer shunt box con- 
taining additional resistance coils connected in such a way that 
when the galvanometer is shunted the total resistance of the 
circuit remains the same as before. In the diagram s 1} s 2 , s 3 are 
the shunt coils ; r 1? r 2 , r 3 the compensating resistances, q. v. 

'Shunt Box, Universal. A shunt box which ma)- be used 
equally well with any galvanometer. 

Siebrosal. A salt to take the place of sal-ammoniac in open 
circuit cells. It is stated that it does not freeze at 12 F., but 



STANDARD ELECTRICAL DICTIONARY. 



621 



assumes a gelatinous condition which does not impair the working 
of the cell. 

Signal, Individual. A signaling device used 'where several 
telephones, for instance, are connected on one circuit. It permits 
of one station calling any one of the others without the call being 
heard at any of the remaining stations. 

Synonym — Selective Signal. 

Sign, Electric. A sign whose letters are formed by placing 
incandescent electric lamps side by side. They are used for adver- 
tising at night. Pretty effects are obtained by various colored 
lamps. 

Sinistrorsal. Left-handed. Applied to the winding of a coil. 

Skew Adjustment of Carbons. A means used in some forms 
of focusing arc lamps to insure the formation of the crater on the 
edge of the positive carbon, so that the most of the light is thrown 
horizontally onto a reflector. It is done by fastening the positive 
carbon out of line with the negative carbon. 

Smashing Point. That point in the life of an incandescent 
lamp at which it is thought to be more economical to replace it by 
a new one than to continue it in use at a continually diminishing 
candle power. The old lamp need not be "smashed/' but may be 
placed where a bright light is not required. 

Source, Electric. 

duce an E. M. F. 



Any arrangement or device which will pro- 



Source, Magnetic. Any arrangement of parts capable of pro- 



ducing lines of magnetic force 




A permanent magnet, lodestone, 
an electro-magnet, or an active 
circuit, may act as a magnetic 
source. (Houston.) 

Splitting the Phase. A method 
used in starting monophase al- 
ternating current motors. 
It consists in superimpos- 
ing upon the alternating 
field an oblique field differ- 
ing in phase. The phase 
of this second field may be 
made to lag by connecting 
an inductive resistance in 
series with its field coil. 



flush 



Fig. 
into the 



Stage Box. 



Stage Box. A box set 

floor of a theatrical stage and having contacts 



622 STANDARD ELECTRICAL, DICTIONARY. 

connected to electric mains, so that a bunch light or other portable 
device may be readily supplied with current by means of a flexible 
cable and a plug which fits the contacts in the box. 

Stand, Rotating, for Galvanometers. A support like a turn- 
table so that a galvanometer placed on it may be readily set in the 
magnetic meridian. By graduating the edge of the rotating part 
in degrees and fixing a pointer to the base, almost any form of 
galvanometer when placed on the stand may be used as a sine 
galvanometer. 

Starting Box. An adjustable rheostat used, in starting a 
motor, to control the current until the counter E. M. F. of the 
motor is of sufficient value to take the place of the resistance. It 
is often provided with automatic electro-magnetic devices which 
cut off the current in case of {a) too much current; (6) lack of 
current. 

Stator. The stationary portion of a rotatory field induction 
motor. It carries the coils which receive the primary current. 

Steam Dynamo. A dynamo driven by direct connection with 
a steam engine. The dynamo may be mounted on the projecting 
crank shaft, or be supported in bearings by an independent shaft 
which is coupled to the engine shaft. 

Steno-Telegraphy. An abbreviated code for sending press 
news. The code consists of single letters, double letters and con- 
tractions of words which represent arbitrarily, figures, words and 
phrases. 

Striking Magnet, (a) An electro-magnet used in an arc lamp 
to separate the carbons a definite distance, when the current is 
turned on, so as to form or " strike " the arc. 

(b) An electro-magnet used to ring a bell, by having a hammer 
attached to its armature. 

Strut. A short pole used to support a line-bearing pole at a 
curve by bearing against it in a direction contrary to the strain. 

Stub, Anchor Guy. A short pole set securely in the ground 
to fasten a guy to. 

Sub=Station. A generating plant subsidiary to a central station ; 
and placed so as to supply current to a district at a considerable 
distance from the main station, or to feed into a network of mains 
at points where the load is greatest. 



STANDARD ELECTRICAL DICTIONARY. 



623 



Sunshine Recorder, Electric. An instrument 
for closing the circuit of a recording apparatus at 
times when the sun's rays fall upon it. The form 
shown in Fig. 382 consists of a differential air ther- 
mometer, the lower bulb coated with lampblack 
and the air in the bulbs being separated by a short 
column of mercury. 

On exposure to solar radiation the air in the 
lower bulb expands the more and forces the mer- 
cury upward where it connects the sealed-in 
electrodes. 

Switch, Automatic, (a) Any switch which 
is not operated directly by a person. 

(b) A form of single pole switch designed to be 
set into a door jamb so that when a door is opened 
a light will be turned on. It is used in clothes 
closets. 

(c) A multi-contact switch operated by an elec- 
tric motor and arranged to make various combin- 
ations of lights in an electric sign or similar 
device. 

Switch, Automatic Telephone. A switch, the 

Electric lever of which is prolonged to form a hook to hang 

Recorder a telephone receiver on. When the receiver is 

hung the call bell is connected in circuit ; when 

the receiver is removed from the hook a spring or weight moves 

the switch and connects the telephone and its battery in circuit. 

Switch, Battery. A plug switch with several 
contacts. It is connected so that any required 
portion ,of a battery may be connected to a 
circuit. 

Switch, Canopy. A switch used on an elec- 
tric street railway car to entirely cut off the 
current from the motors and controllers. There 
are two switches used on each car, one under the 
canopy at each end, connected in series between 
the trolley pole and lightning arrester. The car 
lamps are connected above the canopy switches. 

Switch, Chandelier. A small snap switch in- 
tended to be fastened within the canopy of a chan- 
delier and operated by a pull chain from below. 

Switch, Combination. An arrangement of 
two or more different switches on a single base. 



Fig. 




Fig. 383. 

Chandelier 

Switch. 



624 



STANDARD ELECTRICAL DICTIONARY. 



Switch, Commutation. A double-pole, double throw switch, 
arranged to reverse the connections of a pair of wires. It is used 
in cases where it is desirable to turn on and off a group of lamps 
from a switch at any one of three or more points without regard 
to the setting of the switches at the other points. 



f^ 



-~»- 



~555^_ 



Fig. 384. Commutation Switch. 

As shown in Fig. 384 the end switches are three wire (two point) 
switches, the intermediate ones are the commutation switches. 
The circuit is shown closed. The dotted lines 
show the alternative position of the switches. 
When only two switches are desired, the 
three wire ones alone are used. 

Switch, Double Throw. A knife switch 
having two sets of contacts, one on either 
side of the pivot. 

Switch, Electrolier. A snap switch at- 
tached to an electrolier and having contacts 
arranged so that the lights may be turned 
on one by one, and then off in the same way. 

Switch, Flush. A snap switch whose 
entire mechanism is set in flush w T ith the 
(See App. Wall Box.) 

Switch, Indicating. A snap switch 
showing if its circuit is made or broken by a 
dial bearing the words "ON" and 4 1 OFF. ' ' 

Switch, Intermediate. A switch for 
an intermediate station on a telephone line 
so that the intermediate station may call 
either terminal station, but at other limes 
the main wires are left unbroken. 

Switch, Key. A snap switch arranged 
so that it can only be operated by the use 
F IG# 386. of a suitable key. 

Indicating Switch. Synonym — L,Ock Switch. 




Fig. ; 
Flush Switch. 

wall or wood- work. 




STANDARD ELECTRICAL DICTIONARY. 



625 



Switch, Pendant Pull. A switch which may be turned on or off 
by successive pulls of a cord pendant connected thereto. 

Switch, Push Button. A small portable switch for from one 
to three lights capacity, operated by buttons, and intended to be 
fastened to the end of a flexible cord. 

Switch, Throw-Over. A double 
throw knife switch designed to con- 
nect a three wire system in a build- 
ing either to a three wire street 
main or to a single source on the 
two wire system. The wiring for 
this usage must have the neutral 
equal in cross-section to the sum 
of the tw T o outer wires. It may also 
be used as a break- do w-n switch, 
q. v. 

Switch, Voltmeter. A switch 
whereby a voltmeter may be con- 
nected to any one of a number of 
circuits. 




Fig. 387. Voltmeter Switch. 




Tachometer. An instrument which, by a pointer on a dial, indi- 
cates at any moment the revolutions per minute of a revolving body. 

It comprises a small governor whose 
shaft is rotated by the revolving body. 
The centrifugal force of the governor 
weights is resisted by a helical spring. 
The deflection of the weights operates 
the pointer. The dial is graduated by 
trial. 

Tailings. Prolongations of the 

characters made by a Morse register in 

a system of automatic telegraphy 
Fig. 388. Tachometer. ^^ ^ & hjgh rate of speed Qf 

transmission, the electrostatic capacity of the line gives the signals 
a tendency to run together. 

Telegram. A telegraphic dispatch. 

Telegraphy, Wireless. A mode of electric communication 
without any metallic connection between the stations. It may be 
accomplished in two different ways : First, — the electro-magnetic 
system ; in this, two parallel circuits are established, each circuit 
becoming successively the primary and secondary of an induction 
system, according to the direction in which signals are being sent. 



626 STANDARD ELECTRICAL DICTIONARY. 

Second, — the electric wave system ; in this a suitable radiator sends 
out high-frequency electric waves which act on a suitable relay. 
The first method has operated across five miles, and the second 
across eight miles intervening distance. (See App. Relay, 
Marconi's.) 

Telephone Cabinet, Soundproof. A form of closet containing 
a telephone set, and large enough to hold a person using the 
instrument, so that his conversation may be secret, and also that he 
will not be disturbed by outside noises. 

Synonyms — Silence Cabinet — Telephone Booth. 

Terella. A sphere of lodestone, used by Gilbert in magnetic 
experiments. 
Synonym — Earthkin. 

Test Board. A board provided with switches or spring-jacks 
connected to separate lines, so that testing instruments may be 
readily connected to any particular line. It is used mainly in tele- 
graph and telephone central offices. 

Tester, Cell. A low resistance portable galvanometer or volt- 
meter connected by rubber-covered flexible conductors to two 
insulated contact points, fastened to a handle in such a way that they 
may be readily touched to the terminals of a storage cell in order 
to estimate the charge. Sometimes a low voltage incandescent 
lamp is used instead of a voltmeter for rough tests. 

Tester, Magnetic. An instrument devised by Prof. J. A. Ewing 
for measuring hysteresis in sheet iron. A bundle of the sheet iron 
to be tested is cut to a standard size, the bundle is then placed in a 
holder and rotated between the poles of a pivoted permanent 
magnet, the deflection of which against gravity determines, by 
reference to a table, the hysteresis. 

Testometer. A device used in connection with a burglar alarm 
system whereby, from the central office, an alarm may be brought 
in from any desired building. It uses automatic signal boxes, q.v., 
which may be set in operation by a current sent from the office. 

Tetrapolar. adj. Having four poles : two north and two south 
poles. 

Thermo-Qalvanometer. A galvanometer whose needle is 
suspended in a special form of thermo-electric couple. It is used 
to measure small amounts of radiant energy. (See App. Radio- 
Micrometer. ) 

Time Ball, Electric. A ball dropped from the top of a staff 
prominently placed, in order to indicate some exact moment of 



STANDARD ELECTRICAL DICTIONARY. 627 

mean time. In the United States noon is the time thns indicated, 
and in Great Britain, 1 p. m. The ball is generally released by an 
electro-magnet whose circuit is closed by a standard clock. 

Time Marker. A light flexible stylus actuated by an electro- 
magnet in circuit with an electro-magnetic tuning fork. It is 
used for recording tuning fork vibrations on a chronograph drum. 

Torch, Electric Gas Lighting. A portable apparatus for pro- 
ducing a spark for gas lighting. An induction coil with dry 
battery, an influence machine, or an electrophorus arranged 
within the handle or body of the machine, is set in operation by 
the pressing of a button. A rod attached to the handle carries a 
gas key turner and the spark terminals. 

Synonym — Electric Wand. 

Translator. A form of telephone relay. It consists of a special 
induction coil in which the core wires are about three times the 
length of the coil and are bent back at both ends so as to envelop 
the coils. 

Transmitter, Automatic. An instrument for sending tele- 
graphic messages at a high rate of speed. J^ suitable clockwork or 
electric motor draws a perforated paper strip through a set of 
contacts. The perforations in the strip determine the message. 
(See Telegraph, Automatic — Perforator.) 

Transmitter, Continuity Preserving. A transmitter used in 
Stearns system of duplex telegraphy for changing the connection 
of the line from battery to earth without breaking the circuit. 

Transposition Wires. Short wires used to splice across from 
one line to another where transposition takes place. It is usually 
done at every fourth pole. (See Transposing — in App. Insulator, 
Transposition . ) 

Trimming. The renewal of the carbons in an arc lamp. The 
work of a lamp trimmer frequently includes cleaning the feed rod 
of the upper carbon with a cloth so as to ensure smooth action of 
the clutch. 

In lamps using upper and lower carbons of the same size and 
kind, an economy is effected by placing the short upper carbon 
stub in the lower holder to be further consumed, and placing a new 
carbon above. 

Tube, Crookes'. A hermetically sealed glass vessel provided 
with electrodes sealed through the glass, and containing a high 
vacuum. (See Matter, Radiant.) 



628 



STANDARD ELECTRICAL DICTIONARY. 




Tube, Crookes', Adjustable Vacuum. A 

Crookes' tube in which the degree of vacuum 
may be regulated by heating a suitable chemical 
enclosed in an auxiliary bulb, connected by a 
tube to the main bulb. The small bulb is 
arranged over a small gas or oil burner and the 
vaporization of the chemical regulated by con- 
trolling the burner. 

Tube, Crookes', Focus. A Crookes' tube 
in which the cathode stream emanates from a 
concave electrode and is concentrated upon a 
platinum plate, which may either be the anode 
or be entirely insulated. 

Tube, Crookes', Self = Regulating, {a.) A 

form of adjustable vacuum tube, q. v., in which 
the chemical, whose vaporization alters the 
vacuum, is heated by molecular bombardment 
caused by a discharge in shunt to the main tube 
spark. When the vacuum rises in the main 
tube some of the discharge crosses an air-gap to the heating bulb 
and causes a lowering of the vacuum. The vacuum may be 
adjusted by varying the air-gap. 

(b.) A form of adjustable vacuum 
tube, q. v., in which an electrode is 
sealed in the auxiliary tube contain- 
ing the chemical substance. This 
electrode is connected by a wire or rod 
so placed that its end forms an air-gap 
at the negative terminal of the coil. 
When the vacuum rises in the main 
tube some of the discharge crosses the 
air-gap and decomposes the chemical 
substance in the auxiliary tube, thus 
throwing off minute quantities of vapor 
and lowering the vacuum in the main 
tube. 



Fig. 389. 

Adjustable Vacuum 

Crookes' Focus 

Tube. 




Fig. 39°- 
Self-Regulating 
Crookes' Tube. 



Tubulating. The process of attach- 
ing a small glass tube for exhausting 
to the top of a blown lamp bulb. 

Turbo= Alternator. An alternating 
current dynamo coupled direct to a high-speed steam turbine. 

Turbo=Generator. A generator coupled or geared to a high- 
speed steam turbine, and on the same base with it. 



STANDARD ELECTRICAL DICTIONARY. 



629 



Vibrator, Independent. The interruptor for an induction coil, 
consisting of an electro-magnet with vibrating armature mounted 
on a base with binding posts for connection. 

Volt= Ammeter. An electric measuring instrument wound 
with two coils, of high and low resistance respectively, so that it 
may be used either as a voltmeter or an ammeter. By the simul- 
taneous use of both coils it becomes a wattmeter. 

Voltance. A name proposed by J. T. Sprague for " that energy 
which is convertible into electric energy, and which produces that 
stress, action, or pressure, which we measure in volts and call 
voltage. ' ' 

Volt, International. The legal unit of electromotive force 
defined by the International Congress at Chicago in 1893. It is 
the electromotive force which, steadily ap- 
plied to a conductor whose resistance is one 
international ohm, will produce a current of 
one international ampere, and which is rep- 
resented sufficiently well for practical use by 
\%%% of the electromotive force between the 
poles or electrodes of the voltaic cell known 
as Clark's cell, at a temperature of 15 C. 
(59 F.), and prepared according to certain 
specifications. 

Voltmeter, Multicellular. An electro- 
static voltmeter with a plurality of quadrants 
and vanes, the vanes being all mounted on a 
single axis. The large area of the attracting 
surfaces increases the sensibility of the in- 
strument. They are furnished to indicate a 
potential difference as low as 40 volts. 

Volt Selector. An instrument used 
principally in electro-therapeutics for regu- 
lating currents for cataphoresis. It is on the 
principle of the potentiometer, and in the best forms the E. M. F. 
at the electrodes can be gradually increased from zero to any 
desired amount with perfect smooth- 
ness. 

Wall Box. An iron or steel box de- 
signed to be built into a wall or partition. 
It is open in front to receive a flush switch, 
q. v., or a plug receptacle. Holes in the 
sides of the box admit the ends of interior 
HIE [Fig.' 392. Wall Box. conduits and their wires. 




Fig. 391. 

Multicellular 

Voltmeter. 




630 STANDARD ELECTRICAL DICTIONARY. 

Watch, Non- Magnetic. A watch in which the hair-spring, 
lever and scape- wheel are made of diamagnetic materials. (See 
Paillard Alloys.) 

Synonym — Anti -Magnetic Watch. 

Weber. The practical unit of magnetic flux. It has the value 
of one absolute unit or line. The symbol is <&. The defining 
equation is £=F-t-R, i. e., webers=gilberts -^- oersteds. The 
dimensions equal the square root of the product of force and 
surface, or, 

Vm L T- 2 X L 2 = 2 ^ M L 3 T- 2 = M* l} T' 1 . 

Winder, Magnet. A device for rotating magnet cores, bobbins, 
etc., in order that they may be conveniently rilled with wire. A 
revolution counter is often attached so that the number of turns on 
each bobbin may be known. 

Winding Volume. The cubic contents of the annular winding 
space of a spool or bobbin. It is used in calculating the resistance 
of magnet coils. If V equals the winding volume in cubic centi- 
meters, N equals the ohms in a cubic centimeter of the wire 
selected, and R is the required resistance ; then R=VXN. 

Wire, Annunciator. Wire used for interior wiring of bell and 
annunciator circuits, etc. It is insulated with two oppositely laid 
wraps of cotton saturated with paraffine. The outer covering is 
made in solid colors or a combination of two colors. 

Wire, Bimetallic. A wire composed of two metals. It is made 
with a steel core and a sheathing of copper, thus combining 
strength and conductivity. It is said to be desirable for long dis- 
tant telephone lines. 

Synonym — Composite Wire. 

Wire, Fuse. A soft, readily fusible wire used in cut-outs of 
various kinds. It is made in different sizes, and rated according to 
the largest current it will safely carry. The relation, determined 
by Preece, between the diameter of the wire and the fusing current 
is expressed by the equation 1 = ad 3 / 2 , in which I = current in 
amperes, af=diameter in centimeters, and a=a constant, which for 
a few metals, is here given : — 

Copper, - - - 2530 Tin, - - - 405.5 

Aluminum, - - 1873 Alloy (Tin 1, Lead 2,) 325.5 
German Silver, - 1292 Lead, - - 340.6 



STANDARD ELECTRICAL DICTIONARY. 



631 



Commercial 


fuse wire is sold 


by the 


pound. The 


following 


le shows its size and rating. 








Rated 


Fusing B. & S. 


Rated 


Fusing 


B. &S. 


Capacity. 


Current. No. 


Capacity. 


Current. 


No. 


I 


1-73 30 


40 


54.IO 


IO 


3 


4.89 24 


50 


63.II 


9 


5 


8.99 20 


60 


81.08 


8 


7 


II.32 19 


70 


90.61 


7 


10 


13.84 18 


80 


IOO.5 


ey 2 


15 


19.34 16 


90 


IIO.7 


6 


20 


25.42 14 


IOO 


132. 1 


5 


25 


32.04 13 


125 


154.7 


4 


30 


39.14 12 






(Abbott.) 




Wire Gauge, American. The wire 
gauge which is in standard use in the 
United States for electrical wires. Its 
gauge numbers range from 0000=. 46 inch 
diameter to 40=. 00314 inch diameter 
It is abbreviated A. W. G. 

Synonyms — Brown and Sharpe Gauge 
— B. & S. G. 

Wire Gauge, Birmingham. The 

gauge which is in common use in 
FlG - 393- England for electrical wires. Its gauge 

American Wire Gauge. numbers range from 0000=3.454 inch 
diameter to 36=. 004 inch diameter. It is abbreviated B. W. G. 

Wire Gauge, Edison. A gauge which is in use for sizing 
large conductors. The gauge numbers are proportional to, and 
represent the cross-sectional areas. The numbers give the thou- 
sands of circular mils ; thus, No. 20 is a wire of 20,000 circular 
mils, No. 190 is of 190,000 circular mils; so that a number of twice 
the value of another gives a wire of double the capacity, etc. The 
numbers run by intervals from 3 to 360. It is abbreviated E. S. G. 

Wire, Office. Wire intended for use in a telegraph office to 
connect the instruments and switch-board. It is usually made with 
a wind and a braid of cotton saturated with paraffine. It is some- 
times required with a double or triple cotton braiding. 

Wires, Running Guard. Wires placed parallel to and above 
the trolley wires. Their function is to receive any falling over- 
head wires and prevent their contact with the trolley wire. 

Wires, Span. Wires used to suspend trolley wires. They cross 
the roadway and have insulated clamps to hold the trolley wires. 
At the ends they are supported by side poles. 



632 STANDARD ELECTRICAL DICTIONARY. 

Wires, Span Guard. Wires placed parallel to and above the span 
wires, q. v. They prevent overhead wires from falling on the 
trolley wires. 

Wire, " Superior." A wire of a high resistance alloy. It is 
used for starting boxes, arc lamp rheostats, etc. 

Its specific gravity is 8.4. 

Specific resistance at 20°C. (68°F.) 86 microhms. 

Resistance per mil-foot at 20 C. ( 68° F.) 517.5 ohms. 

Approximate percentage increase of resistance per i°C. (i.8° F.) 
at about 20 C. (68° F.), 0.065 per cent. 

Wire, Tie. A short piece of wire used to secure a conductor to 
an insulator. 

Zero Instrument. An instrument in which the value of the 
quantity being measured is shown by the arrangement of the 
essential parts of the instrument when an indicator connected 
with the instrument points to zero. Wheatstone's Bridge and the 
potentiometer are instruments of this class. (See Null Method.) 



INDEX. 



Page. 

A 7 

Absolute, 7 

Absolute Calibration, ... 91 
Absolute Electric Potential, . . 429 
Absolute Electrometer, . . 222 
Absolute Galvanometer, . . 266 

Absolute Measurement, . . 8 

Absolute Potential, .... 423 
Absolute Temperature, . . S 

Absolute Unit, 554 

Absolute Unit Resistance, Weber's 46S 
Absolute Vacuum, .... 557 
Absolute Zero, . . . . 5S1 

Abscissa, 7 

Abscissas, Axis of . . . . 54 
Absorption, Electric 
A. C. C. 



Acceleration, 
Accumulator, . 
Accumulator, Electrostatic 
Accumulator, Water Dropping 
Acetic Acid Battery 
Acheson Effect 
Acid, Caroonic 
Acid, Chromic, Battery 
Acid, Hydrochloric, Battery- 
Acid, Spent .... 
Acid, Sulphuric 
Acidometer, . 
Acierage, . 
Aclinic Line . 
Acoustic Telegraphy 
Acoutemeter . 
Action, Electrophoric 
Action, Local . 
Action, Magne-crystallic 
Action, Refreshing 
Action, Secondary . 
Actinic Photometer, 
Actinic Rays. . 
Actinism, 

Actinometer, Electric 
Active Electric Circuit, 
Activity, 

Actual Horse Power, . 
Adapter, 

A. D. C 

Adherence, Electro-magnetic 
Adherence, Magnetic . 
Adjuster, Cord 
Adjustment of Brushes, 
Admiralty Rules of Heating, 
^Eolotropic, .... 



58 

208 

108 

61 

66 

491 

497 

10 

494 

10 

10 

10-53 

230 

381 

385 

454 

477 

411 

11 

11 

11 

123 

11 

290 

11 

11 

11 

33 S 

152 

90 

12 

34 



Aerial Cable, 
Aerial Conductor, 

Affinity, 

Affinity, Molecular 
After Current, .... 
Agglomerate Leclanche Battery, 
Agir Motor .... 

Agone, 

Agonic Line, .... 

Air, 

Air Blast, 

Air Condenser, 

Air Field, 

Air Gaps. .... 

Air Line Wire 

Air Pump, Heated 

Air Pump, Mercurial 

Air Pumps, Short Fall . 

Alarm, Burglar 

Alarm, Electric 

Alarm, Fire Electric Automatic 

Alarm, Fire and Heat . 

Alarm, Overflow . 

Alarm, Water Level 

Alcohol, Electric Rectification of 

Alignment, .... 

Allotropy, 

Alloy, 

Alloy, Platinum 
Alloy, Platinum— Silver, 
Alloys, Paillard 
Alphabet, Telegraphic 
Alternating, .... 
Alternating Current, . 
Alternating Current Arc, 
Alternating Current Dynamo, 
Alternating Current Generator 

Dynamo, .... 
Alternating Current Meter, . 
Alternating Current System, 
Alternating Field, . 
Alternative Current, 
Alternative Path, 
Alternatives, Voltaic . 
Alternator, .... 

Alternator, Constant Current 
Alternator, Dead Point of an . 
Alternation, .... 
Alternation, Complete 
Alternation, Cycle of . 
Alum Battery, .... 
Aluminum, .... 
Aluminum Battery, . 



Page. 
. 95 
12 
. 12 
380 
. 159 



. 13 

13 

, 13 

13 
, 13 

14 
. 252 

15 
, 15 

15 
, 16 

16 
, 16 

17 
257 

17 
, 18 

18 
, 18 

18 
, 18 

18 

419 

, 419 

, 400 

19 

, 23 

159 

23 
193 

24 

373 

23 

252 

563 

24 

563 

24 

24 

177 

23 

23 

175 

58 

24 

5$ 



%4 



INDEX. 



Page. 
Amalgam, 24 

Amalgamation, . . .25 

Amber, 25 

American Twist Joint, . 309 

Ammeter, 26 

Ammeter, Ayrton . . . .26 
Ammeter, Commutator . . 26 
Ammeter, Cunynghame's . . 26 
Ammeter, Eccentric Iron Disc, . 27 
Ammeter, Electro-magnetic . . 27 
Ammeter, Gravity ... 27 
Ammeter, Magnetic Vane . . 27 
Ammeter, Magnifying Spring . 28 
Ammeter, Permanent Magnet . 28 
Ammeter, Reducteur for . . 453 
Ammeter, Solenoid . . . .28 
Ammeter, Spring .... 28 
Ammeter, Steel Yard ... 28 
Ammunition Hoist, Electric . 29 

Amperage, 29 

Ampere, 29 

Ampere- and Volt-meter Galva- 
nometer, 274 

Ampere Arc, 30 

Ampere Balance, .... 56 
Ampere Currents, . . . .30 
Ampere Feet, .... 30 

Ampere-hour, 30 

Amperes, Lost .... 30 
Ampere's Memoria Technica . 30 

Ampere Meters, .... 26-30 
Ampere Meter, Balance . . . 391 
Ampere Meter, Neutral Wire . 391 
Ampere-minute, . . . .30 
Ampere Ring, .... 30 
Ampere-second, . . . .30 

Ampere's Theory of Magnetism, 354 
Ampere-turns, . . . .31 

Ampere-turns, Primarv . . 31 
Ampere-turns, Secondary . 31-551 
Ampere Windings, ... 31 
Amperian Currents, . . . 165 

Amplitude of Waves, ... 31 
Analogous Pole, ... . 31-425 

Analysis, 31 

Analysis, Electric . . . .32 
Analysis, Electrolytic . . . 214 
Analyzer, Electric . . . .32 

Anelectrics, 32 

Anelectrotonus, . . . .32 

Angle of Declination, . . 32-177 

Angle of the Polar Span, . . 32 

Angle of Inclination or Dip, . 33 
Angle of Lag, .... 33-318 
Angle of Lead, .... 33 
Angle of Maximum Sensitiveness, 479 
Angle of Polar Span, . . . 423 

Angle, Polar 423 

Angle, Unit 554 

Angular Currents, .... 165 
Angular Currents, Laws of .165 

Angular Force, .... 544 



Page, 

Angular Velocity, . . 32-559 

Animal Electricity, . . . .33 
Animal System, Electric Excita- 
bility of . . ; . . .247 

Anion, 33 

Anisotropic, 34 

Annealing, Electric . . . ' 34 
Annular Electro-magnet, . .216 

Annunciator, 34 

Annunciator Clock, . . . .35 
Annunciator Clock, Electric . 127 
Annunciator Drop, . . . .35 
Annunciator, Gravity Drop . 35 

Annunciator, Needle . . .35 
Annunciator, Swinging or Pendulum 35 
Anodal Diffusion, . . . .35 

Anode, 86 

Anodic Closure Contraction, . . 36 
Anodic Duration Contraction, 
Anodic Opening Contraction, 
Anodic Reactions, 
Anomalous Magnet, 
Anti-induction Conductor . 
Anti-magnetic Shield, 
Antilogous Pole, . 
Antimony, .... 

Anvil, 

A. O. C 

Aperiodic, .... 
Aperiodic Galvanometer, 
Apparent Coefficient of Magnetic 

Induction, 346 

Apparent Resistance, . . 297-462 
Apparent Watts, . . .573 

Arago's Disc, 



. 36 

36 

. 335 

36-145 

. 37 

425 

. 37 

37 



266 



Arc, 


. 39 


Arc, Ampere 


30 


Arc, Compound 


. 39 


Arc, Electric Blow-pipe 


84 


Arc, Metallic .... 


. 39 


Arc, Micrometer . 


39-376 


Arc, Multiple .... 


. 387 


Arc, Simple .... 


39 


Arc, Voltaic .... 


. 39 


Arc Box, Multiple 


387 


Arc Lamp, .... 


. 319 


Arc Lamp, Differential 


. 320 


Arc Lamp, Double Carbon 


. 191 


Areometer, .... 


41 


Areometer, Bead 


. 41 


Argyrometry, 


41 


Arm, 


. 41 


Armature, .... 


41 


Armature, Bar .... 


. 42 


Armature, Bipolar 


42 


Armature Bore, . . . 


. 42 


Armature Chamber, 


42 


Armature, Closed Coil 


. 43 


Armature Coil, or Coils 


43 


Armature Conductors, Lamii 


la- 


tion of .... 


, 319 


Armature Core, . 


43 



INDEX. 



635 



Armature, Cylinder 
Armature, Cylindrical 
Armature, Disc 
Armature, Drum . 
Armature Factor, 
Armature, Flat Ring . 
Armature, Girder 
Armature, H 
Armature, Hinged . 
Armature, Hole 
Armature, Intensity 
Armature Interference, 
Armature, Load of . 
Armature, Multipolar . 
Armature, Neutral . 
Armature, Neutral Relay 
Armature, Non-polarized 
Armature of Influence Machine, 
Armature of Leyden Jar or Static 

Condenser, 
Armature, Open Coil 
Armature, Perforated 
Armature, Pivoted 
Armature Pockets, 
Armature, Polarized 
Armature, Pole 
Armature, Quantity 
Armature ^Radial 
Armature Reactions. 
Armature, Revolving, Page's 
Armature, Ring . 
Armature, Rolling 
Armatures, Gyrostatic Action 
Armature, Shuttle 
Armature, Siemens' Old . 
Armature, Spherical 
Armature, Stranded Conducto 
Armature, Unipolar 
Armature, Ventilation of 
Armor of Cable, 
Arm, Rheostat 
Arms, Proportionate 
Arms, Ratio . 
Arms, Rocker . 
Arrester, Lightning 
Arrester, Lightning, Counter 

tro-motive Force 
Arrester, Lightning, Plates 
Arrester, Lightning, Vacuum 
Arrester Plate, 
Arrester, Spark 
Arrival Curve, 
Articulate Speech, 
Artificial Carbon, 
Artificial Magnet, . 
Ascending Lightning, 
Assymmetrical Resistance, 

Astatic, 

Astatic Circuit, 
Astatic Couple, 
Astatic Galvanometer, 
Astatic Needle. 



Page. 
. 43 



of 



elec- 



45 
. 43 

45 
. 45 

45 
. 49 

49 
. 45 

45 
. 45 

45 
. 46 

46 

. 46 

46-390 

. 46 

46 

46 

46 

. 45 

47 

. 4T 

47 

. 47 

47 

. 47 

47 

. 47 

48 

. 49 

2S3 

49 

. 49 

49 

. 49 

50-553 

560 

. 50 

472 

. 436 

437 

50-474 

328 



329 
329 
329 
417 
4S9 
16S 

50 
106 
335 
330 
462 

50 

12 
157 
266 

50 



52-285 

. 53 

52 

. 223 

53 

. 52 

338 

. 380 

380 



Page. 
Astronomical Meridian, . . . 372 

Asymptote, 51 

Atmosphere, . . . ... 51 

Atmosphere, Residual . . 51-460 

Atmospheric Electricity, . . 5l 

Atom, 52 

Atomic Attraction, . . . .52 
Atomic Current* .... 160 
Atomic Energy, 
Atomic Heat, 
Atomic Weight, 
Atomicity, .... 
Attracted Disc Electrometer, 
Attraction, .... 
Attraction, Atomic . 
Attraction, Magnetic . 
Attraction, Molar 
Attraction, Molecular . 
Attraction and Repulsion, Electro- 

dvnamic 211 

Attraction and Repulsion, Electro- 
magnetic 217 

Attraction and Repulsion, E ectro- 

static 234 

Attraction and Repulsion, Electro- 
static, Coulomb's Law of . 155 

Audiometer, 53 

Aura, Electrical .... 53 

Aurora, 53 

Austral Pole, .... 54 

Autographic Telegraph, . . . 510 
Automatic Circuit Breaker, . 121 

Automatic Cut Out, . . . 175-475 
Automatic Drop, . . . .192 
Automatic Electric Bell. . . . 78 
Automatic Electric Fire Alarm, . 257 
Automatic Switch, .... 500 
Automatic Telegraph, . . . 504 

A. W. G 54 

Axial Couple, .... 544 

Axial Force, 544 

Axial Magnet, . . . . 336 

Axis, Electric 54 

Axis, Magnetic .... 338 
Axis of Abscissas, .... 54 
Axis of Ordinates, . . 54-397 

Axis of X 54 

Axis of Y 54-397 

Ayrton's Ammeter, ... 26 

Azimuth 54 

Azimuth Circle, .... 54 
Azimuth Compass, . . . .141 
Azimuth, Magnetic . . . 338 

B, 55 

B. A 55 

Back Electro-motive Force of Po- 
larization, .... 156 
Back Induction, .... 55 
Back Shock or Stroke of Lightning, 55 

Back Stroke, 55 

Bagration Battery, ... 59 



w 



INDEX. 



Balance, . . . 

Balance, Ampere . 

Balance Ampere Meter, 

Balance, Electric . 

Balance, Inductance 

Balance, Plating . 

Balance, Slide . 

Balance, Thermic 

Balance, Torsion, Coulomb's 

Balance, Wheatstone's . 

Balata, 

Ballistic Galvanometer, 

Balloon Battery, 

B. and S. W. G. 

Banked Battery, 

Bank of Lamps, 

B. A. Ohm, . 

Barad, 

Bar, Armature 

Bar, Bus 

Bar Electro-magnet, 

Bar Magnet, . 

Barometer, 

Bar, Omnibus 

Bar Photometer, 

Bars, Commutator • 

Bath, . 

Bath, Bipolar Electric 

Bath, Copper 

Bath, Copper Stripping 

Bath, Electric Head 

Bath, Electric Shower 

Bath, Gold 

Bath, Gold Stripping . 

Bath, Multipolar Electric 

Bath, Nickel . 

Bath, Plating . 

Baths, Electro-medical 

Bath, Silver . 

Bath, Silver Stripping 

Bath, Stripping 

Bath, Unipolar Electric 

Batten, .... 

Battery, Acetic Acid 

Battery, Alum 

Battery, Alumnium . 

Battery, Bagration 

Battery, Balloon 

Battery, Banked . 

Battery, Bichromate 

Battery, Bunsen 

Battery, Cadmium . 

Battery, Callan 

Battery, Camacho's . 

Battery, Carre's 

Battery, Cautery 

Battery Cell, Element of 

Battery, Chloric Acid 

Battery, Chloride of Lime 

Battery, Chromic Acid 

Battery, Closed Circuit 

Battery, Column 



Page. 

. 55 

56 

. 391 

577 

. 293 

417 

. 374 

85 

. 544 

577 

. 56 

567 

. 59 

. 56 

59 

. 323 

394 

. 56 

42 

. 94 

217 



. 56 

94 

. 411 

56-140 

. 57 

57 

. 152 

152 

. 284 

57 

. 279 

279 

. 57 

391 

. 418 

222 

4S4 

. 484 

57 

. 57 

57-58 

. 58 

58 

. 58 

59 

. 59 

59 



60 
60 
60 
60 
61 
237 
61 
61 
61 
61 
61 



62 
179 
63 
63 
63 
63 



281 
64 
64 
65 
65 
66 



66 
. 66 

66 

. 66 

66-331 



Page, 

Battery, d'Arsonval's . 

Battery, de la Rue . 

Battery, de la Rive's Floating. . 

Battery, Dry .... 

Battery, Elements of 

Battery, Faradic .... 

Battery, Ferric Chloride 

Battery, Fuller's .... 

Battery, Gas .... 

Battery, Gas, Grove's 

Battery Gauge, 

Battery, Gravity .... 

Battery, Grenet 

Battery, Grove's .... 

Battery, Hydrochloric Acid 

Battery, Lalande & Chaperon 

Battery, Lalande-Edison 

Battery, Lead Chloride 

Battery, Lead Sulphate . 

Battery, Leclanche 

Battery, Leclanche Agglomerate 

Battery, Local 

Battery, Magnetic 

Battery, Main .... 

Battery, Marie Davy's 

Battery, Maynooth's 

Battery, Medical 

Battery, Meidinger's . „ 

Battery, Mercury Bichromate 

Battery Mud, .... 

Battery, Multiple Connected . 

Battery, Niaudet's 

Battery, Nitric Acid 

Battery of Dynamos, . 

Battery of Leyden Jars, 

Battery, Open Circuit . 

Battery or Pile, Thermo-electric 

Battery, Oxide of Copper . 

Battery, Peroxide of Lead 

Battery, Platinized Carbon . . 69 

Battery, Plunge . . . .69 

Battery, Pneumatic ... 69 

Battery, Primary . . . 69-434 

Battery, Pulvermacher's Electro- 
medical 69 

Battery, Sal Ammoniac . . 69 

Battery, Salt, or Sea Salt, 

Battery, Sand .... 

Battery, Secondary .... 

Battery, Secondary, Plante's 

Battery, Secondary, Real Efficiency 
of 

Battery, Sir William Thomson's 

Battery, Siemens and Halske's . 

Battery, Skrivanow 

Battery, Smee's .... 

Battery Solutions, Chromic Acid 

119-178-192-232-318-421-542-549 

Battery, Spiral 73 

Battery, Split .... 73 

Battery, Sulphate of Mercury . 67 

Battery System, Universal . . 556 



61 



530 
68 



70 
70 

72 

205 

72 
72 
72 
73 
73 



INDEX. 



6 37 



Page. 
Battery, Thermo-chemical . . 580 
Battery, Trough .... 73 
Battery, Trouve's Blotting Paper 73 
Battery, Tyer's .... 74 
Battery, Upward's . . . .75 
Battery, Varley's .... 76 
Battery, Volta's . . . .76 

Battery, Voltaic or Galvanic . 76 
Battery Voltmeter, . . . .569 
Battery, Water .... 77 
Battery, Wollaston . . . .78 

B. A. Unit, 554 

B. A. Unit of Resistance, . 78-462 
B. A. Volt, . . . . .568 

B. E 78 

Bead Areometer, .... 41 
Becquerel's Laws of Thermo-elec- 
tricity 78 

Beaume Hydrometer, . . .78 

Bed-piece, 78 

Bell, Automatic Electric . . 78 

Bell, Call 7S-98 

Bell Call, ..... 79 

Bell Call, Extension . . . .248 
Bell, Circular .... 79 

Bell, Differentially Wound . . 79 
Bell, Electric .... 79 

Bell, Electro-mechanical . . 80 

Bell, Indicating . . . 80-297 

Bell, Magneto 80 

Bell, Magneto Call . . .361 

Bell, Night 392 

Bell-shaped Magnet, . . .336 
Bells, Relay .... 80-457 
Bell, Trembling .... 78 
Bell, Vibrating .... 78 

Belts, Joints in .... 311 
Bennett's Electroscope, . . . 233 

Bias 80 

Bias of Tongue of Polarized Relay, 542 

59 

. 63 
. 498 

. 81 
81 

. 81 
81 

. 81 
. 208 

. 82 
42 

. 57 
. 132 

. 82 
82-524 

.419 



Bichromate Battery, 

Bichromate Mercury Battery, 

Bifilar Suspension, 

Bifilar,Winding, 

Binary Compound, 

Binding, 

Binding Posts or Screws, 

Binnacle, 

Biology, Electro- . 

Bioscopy, Electric 

Bipolar Armature, 

Bipolar Electric Bath, 

Bisected Coils, 

Bismuth, 

Bi-telephone, 

Black, Platinum 

Blasting, Electric 

Bleaching, Electric 

Block, Branch 

Block, Cross-over 

Block System, 

Block Wire, 



87 
158 



Page. 
Blotting Paper Battery, Trouve's 73 

Blow-pipe, 83 

Blow-pipe, Electric Arc . . 84 

Blue Magnetism, .... 355 

Bluestone, 

Blue Vitriol, 

Board, Cross-connecting 

Board, Fuse 

Board, Hanger 

Board, Key 

Board, Multiple Switch 

Board of Trade Ohm, 

Board of Trade Unit, . 

Board, Switch . 

Boat, Electric 

Bobbins, 

Body Protector, 

Bohenberger's Electroscope, 

Boiler Feed, Electric 

Boiling, .... 

Boll, .... 

Bolometer, 

Bombardment, Molecular 

Bore, Armature 

Boreal Pole, . 

Bdt, . 

Bound Charge, 

Box Bridge, 

Box, Cable 

Box, Cooling 

Box, Distributing 

Boxes, Flush 

Box, Fishing . 

Box, Fuse 

Boxing the Compass 

Box, Junction . 

Box, Multiple Arc 

Box, Resistance 

Box, Resistance, Sliding 

Box Sounding Relay, 

Box, Splice 

Bracket, Saddle 

Bracket, Wall 

Braid, Tubular . . . 

Brake, Electro-magnetic 

Brake, Magneto-electric . 

Brake, Prony . 

Branch, .... 

Branch Block, 

Branch Circuit, 

Branch Conductor, 

Branding, Electric . 

Brassing, . 

Brazing, Electric 

Break, .... 

Break, Circuit Loop 

Break-down Switch, 

Breaker, Automatic Circuit 

Breaker, Circuit 

Breaker, Circuit, File 

Breaker, Contact . 

Break Induced Current, . 



6& 



INDEX. 



Breaking Weight, 

Break, Loop 

Break Shock, . 

Breath Figures, Electric 

Breeze, Electric 

Breeze, Static 

Breguet Unit of Resistance, 

Bridge, .... 

Bridge, Box . 

Bridge, Inductance . 

Bridge, Induction 

Bridge Key, 

Bridge, Magnetic . 

Bridge, Meter . 

Bridge, Resistance 

Bridge, Reversible . 

Bridge, Slide . 

Bridge, Wheatstone . 

Bridge, Wheatstone, Commercial 

British Association Bridge, 

Britannia Joint, 

Broadside Method, . 

Broken Circuit, 

Bronzing, .... 

Brush, .... 

Brush, Carbon . 

Brush, Collecting . 

Brush, Discharge 

Brushes, Adjustment of 

Brushes, Lead of 

Brushes, Negative Lead of 

Brushes, Scratch 

Brush, Faradic 

Brush Holders, . 

Brush, Pilot . 

Brush, Rotating 

Brush, Third . 

Brush Trimmer, 

Brush, Wire Gauge 

Buckling, . 

Bug, . . . 

Bug Trap, . 

Bunched Cable, 

Bunsen Battery, 

Bunsen Disc, 

Bunsen's Photometer 

Buoy, Electric . 

Burglar Alarm, 

Burner, Electric Gas 

Burning, 

Bus Bar, 

Bus Rod, 

Bus Wire, . 

Butt Joint, 

Button, Call 

Button, Press 

Button, Push 

Buzzer, . 

B.W. G., . 



Page. 



C, 

c.c, 



332 

482 

, 89 

89 

, 493 

463 

, 89 

89 

, 293 

293 

, 313 

338 

. 3T3 

577 

, 472 

374 

, 575 

36 

, 89 

309 

89 

125 

. 89 

90 

90 

90 

, 187 

90 

, 90 

324 

476 

251 

. 91 

91 

. 91 

91 

549 

92 

, 92 

92 

, 92 

, 95 

59 

92 

412 

93 

16 

93 

94 

94 

94 

94 

310 

98 

94 

)3-98 

94 

94 

95 
109 



Cable, 

Cable, Aerial . 

Cable, Armature of 

Caole, Armor of 

Cable Box, 

Cable, Bunched 

Cable, Capacity of 

Cable Clip, 

Cable Core, 

Cable, Duplex 

Cable, Flat 

Cablegram, 

Cable Grip, 

Cable Hanger, 

Cable Hanger Tongs, 

Cable, Suspension Wire o 

Cable Tank, 

Cadmium Battery, 

Calamine, . 

Cal Electricity, 

Calibration, 

Calibration, Absolute . 

Calibration, Invariable 

Calibration, Relative . 

Call Bell, . 

Call Bell, Extension 

Call Bell, Magneto . 

Call Button, . 

Call, Thermo . 

Call, Thermo-electric . 

Callan Battery . 

Calling Drop, 

Calorie or Calory, 

Calorimeter, . 

Calorimetric Photometer, 

Calory or Calorie, 

Cam, Listening 

Camacho's Battery, 

Candie, 

Candle, Concentric 

Candle, Debrun 

Candle, Decimal . 

Candle, Electric 

Candle-foot, . 

Candle, German Standard 

Candle Holder, 

Candle, Jablochkoff . 

Candle, Jamin 

Candle, Meter . 

Candle Power, 

Candle Power, Nominal 

Candle Power, Rated . 

Candle Power, Spherical 

Candle, Standard . 

Candle, Wilde . 

Caoutchouc, . 

Cap, Insulator . 

Capacity, Carrying 

Capacity, Dielectric . 

Capacity, Electric or Electrostatic 

Capacity, Instantaneous 

Capacity, Magnetic Inductive 



Page. 
95 



97 
97 
97 
60 

97 

208 

97 

97 

97 

98 

78-79-98 

248 

. 361 

98 

. &30 

531 



95 
50 
50 
95 
95 
95 
97 
96 
96 
96 
96 
96 



98 



98 
412 



60 
99 
99 
99 

99 



259 
99 
99 
100 
100 
374 
100 
101 
101 
101 
101 
101 
101 
306 
108 
102 
102 
102 
346-349 



INDEX. 



639 



Page. 

Capillarity, Electro- . . . 209 
Capillary Electrometer, . . . 224 
Capacity of a Telegraph Conduc- 
tor, 103 

Capacity of Cable, . . . .95 
Capacity of Polarization of a Vol- 
taic Cell 103 

Capacity, Polarization . . . 424 
Capacity, Residual .... 103 
Capacity, Specific Inductive . 103 
Capacity, Storage . . . 105-495 
Capacity, Unit of . . . . 105 

Capillarity, 105 

Capillary Telephone, . . . 525 

Carbon, 106 

Carbon, Artificial .... 106 

Carbon Brush, 90 

Carbon, Concentric . . . 107 

Carbon, Cored 107 

Carbon Dioxide, .... 107 
Carbon Holders, . . . .107 
Carbonic Acid, .... 108 
Carbonic Acid Gas, .... 108 
Carbonization, . . . .107 

Carbonized Cloth 107 

Carbon, Platinized, Battery . 69 

Carbon Resistance, .... 463 
Carbon, Retort . . . .471 
Carbons, Lamp, Flashing of Incan- 
descent . . . .257 
Carbon, Telephone . . . .525 
Carbon Transmitter, . . . 549 
Carbon, Volatilization of . . 108 
Carburetted Hydrogen, Heavy . 397 

Carcel 108 

Carcel Gas Jet, .... 108 

Carcel Lamp, 108 

Card, Compass .... 142 
Cardew Voltmeter, .... 569 
Carry's Battery, .... 60 
Carrying Capacity, .... 108 

Cascade, 108 

Cascade, Charging and Discharg- 
ing Leyden Jars in . .108 
Cascade, Gassiot's .... 275 
Case-hardening, Electric . . 109 

Cataphoresis, 109 

Catch, Safety 175 



Cathode, etc. See Kathode, 

Caustry, Galvano 

Cautery Battery, 

Cautery, Electric . 

Cautery, Galvano 

Cautery, Galvano-electric . 

Cautery, Galvano-thermal 

Cell, Battery, Element of a . 

Cell, Constant .... 

Cell, Electrolytic . 

Cell, Porous .... 

Cell, Selenium . 

Cell, Standard Voltaic 

Cell, Standard Voltaic, Daniells' , 



312 
109 
61 
109 
109 
109 
109 
237 
109 
109 
427 
478 
109 
109 



Cell, Standard Voltaic 
Clark's .... 

Central Station .... 

Central Station Distribution 
Supply, .... 

Centre of Gravity, 

Centre of Gyration, 

Centre of Oscillation, 

Centre of Percussion, . 

Centrifugal Force, . 

Centrifugal Governor, . 

C. G. S. 



Page. 
Latimer 

110 
493 



Chain, Molecular . 
Chamber, Armature . 
Chamber of Incandescent Lamp 
Change, Chemical 
Changer, Pole 
Changing Over Switch, . 
Changing Switch, . 
Chaperon, Lalande &, Battel y 
Characteristic 
Characteristic Curve, 
Characteristic Curve, External 
Characteristic Curve of Converter, 169 
Characteristic, Drooping . . 114 
Characteristic, External . . .114 
Characteristic, Internal . . 114 
Characteristics of Sound, . .114 

Charge, 114 

Charge and Discharge Key . . 313 
Charge, Bound . . . .115 
Charge Current, . . . .160 
Charge, Density of . . 115-180 
Charge, Dissipation of . . .115 
Charge, Distribution of . . 115 

Charge, Free 115 

Charge, Negative . 
Charge, Residual 
Charging Curve, . 
Chatterton's Compound, 
Chemical Change, 
Chemical Electric Meter, 
Chemical, Electro-, Equivalents 
Chemical Element, . 
Chemical Energv, 
Chemical Equivalent, 
Chemical, Cautery Galvano 
Chemical Recorder, . 
Chemical Telephone, 
Chemical Equivalent, Thermo- 
chemistry, .... 
Chemistry, Electro- . 
Cheval, Force de . 

Chicle, 

Chimes, Electric . 
Chloric Acid Battery, 
Chloride, Ferric, Battery 
Chloride, Lead, Battery . 
Chloride of Lime Battery, . 
Chlorimeter, .... 
Choking Coil, 
Chronograph, Electric 



112 
112 
112 
112 
112 
112 
113 
113 
3S0 
42 
113 
116 
425 
500 
500 
69 
169 
1-168 
171 



116 
170 
116 
116 
375 
244 



244 

265 

117 

526 

245 

118 

209 

260 

56 

118 

61 

63 

66 

61 

73 

132 

118 



640 



INDEX. 



Page. 
Chromic Acid Battery, ... 61 
Chromic Acid Battery Solutions, . 73 
Chromoscope, . . . .119 

Chutaux's Solution, .... 119 

Cipher Code, 130 

Circle, Azimuth . . . .54 

Circle, Delezenne's . . . 133 
Circle, Galvanic or Voltaic . .119 

Circle, Magic 119 

Circuit, 120 

Circuit, Astatic .... 120 
Circuit, Branch . . . .121 

Circuit Breaker, . . . . 121 
Circuit Breaker, Automatic . . 121 
Circuit Breaker, File . . .121 
Circuit Breaker, Mercury . . 121 
Circuit Breaker, Pendulum . 121 

Circuit Breaker, Tuning-fork . . 121 
Circuit, Broken .... 125 
Circuit Changing Switch, . . 500 
Circuit, Closed, Battery . . 61 
Circuit, Derivative .... 123 
Circuit, Derived . . . .123 
Circuit, Electrostatic . . . 123 
Circuit, Electric, Active . . 123 
Circuit, External .... 123 
Circuit, Grounded . . . 123 

Circuit, Incomplete .... 125 

Circuit Indicator 298 

Circuit Induction, Open . . . 303 
Circuit, Leg of .... 325 

Circuit, Local 331 

Circuit, Loop 125 

Circuit, Loop Break .... 125 
Circuit, Magnetic .... 340 
Circuit, Magnetic Double . . 340 

Circuit, Main 125 

Circuit, Main Battery . . .125 
Circuit, Metallic . . . .125 
Circuit, Negative Side of . . 125 

Circuit, Open . . . . 125 

Circuit, Positive Side of . . . 125 
Circuit, Recoil .... 125 

Circuit, Return 125 

Circuits, Forked . . . .126 

Circuit, Short 482 

Circuit, Shunt . . . 123-126 

Circuit, Simple 126 

Circuits, Parallel . . . 123-126 

Circuit, Voltaic 126 

Circuit Working, Short . . 482 

Circular Bell 79 

Circular Current, . . . .160 

Circular, Mil 379 

Circular Units, . . . 126-555 
Circumflux, . . . . .126 

Clamp, 126 

Clark's Compound, . . . .126 
Cleansing, Fire . . . .257 
Clearance Space, .... 489 
Cleat, Crossing . . . .127 
Cleats, 127 



Page. 
Cleavage, Electrification by . 127 

Clip, Cable 97 

Clock, Annunciator ... 35 
Clock, Controlled .... 127 
Clock, Controlling . . .127 
Clock, Electric Annunciator . . 127 
Clock, Electrolytic ... 128 

Clock, Master 127 

Clock, Secondary .... 127 
Clock, Self-winding, Electric . . 128 
Clockwork Feed, . . . .128 

Cloisons, 128 

Closed Circuit Battery, . . 61 
Closed Coil Armature, ..." 

Closure, 

Closure Contraction, Kathodic 
Cloth, Carbonized .... 
Club-foot Electro-magnet, . 

Clutch, 

Clutch, Electro-magnetic 
Coatings of a Condenser, or Prime 

Conductor, .... 129 
Cockburn Fuse, . . . .263 

Code, Cipher 130 

Code, S. N., 486 

Code, Telegraphic . . 130-511 

Coefficient, 130 

Coefficient, Apparent, of Magnetic 

Induction .... 346 
Coefficient, Economic . 130-204-205 
Coefficient of Electrical Energy, 205 
Coefficient of Expansion, . . 247 
Coefficient of Induced Magnetiza- 
tion, 359-354 

Coefficient of Magnetic Induc- 
tion, 346-349 



128 
312 
107 

217 
128 
128 



Coefficient of Mutual Induction, 


301 


Coefficient of Self-induction, . 


. 298 


Coercitive Force, . 


471 


Coercive Force, 


. 471 


Coercive or Coercitive Force, 


131 


Coil and Plunger, 


. 131 


Coil and Coil Plunger, . 


131 


Coil and Plunger, Differential 


. 132 


Coil, Armature 


43 


Coil, Choking .... 


. 132 


Coil, Earth .... 


133 


Coil, Electric .... 


.133 


Coil, Exploring 


350 


Coil, Flat 


. 133 


Coil, Induction 


133 


Coil, Induction, Inverted 


. 136 


Coil, Induction, Telephone . 


137 


Coil, Kicking .... 


. 132 


Coil, Magnet .... 


336 


Coil, Magnetizing 


. 137 


Coil, Reaction 


132 


Coil, Resistance 


. 137 


Coil, Resistance, Standard . 


464 


Coil, Rhumkorff 


. 138 


Coil, Ribbon .... 


138 


Coils, Bisected .... 


- 133 



INDEX. 



641 



Page. 

Coils, Compensating . . . 138 
Coils, Sectioned .... 138 

Coils, Henry's .... 138 

Coils, Idle 295 

Coil, Single, Dynamo . . . 202 

Coil, Spark 489 

Coil. Sucking 132 

Collecting Brush, .... 90 
Collecting Ring, .... 139 

Collector, 139 

Colombin, 139 

Colophony 460 

Colors of Secondary Plates, . . 478 
Column Battery, .... 61 
Column, Electric . . . . 139 

Comb 140 

Combined Resistance, . . . 464 
Comb Protector, .... 437 
Commercial Efficiency, . . . 204 
Commercial Efficiency of Dynamo, 195 
Commercial Wheatstone Bridge, . 86 
Common Reservoir, . . . 460 

Communicator, 140 

Commutation, Diameter of . . 182 
Commutator, .... 140 

Commutator Ammeter, . . 26 

Commutator Bars, . . . 140-56 
Commutator, Flats in . . . 140 
Commutator, High Bars of . . 289 
Commutator, Neutral Line of . 390 
Commutator, Neutral Point of . 390 
Commutator of Current Generators 

and Motors, . . . .140 

Commutators, Bars of . . . 56 
Commutator Segments, . . .56 
Commutator, Split Ring . . 141 
Commuted Current, .... 160 

Commuter, 140 

Commuting Transformer, . . 547 

Compass, 141 

Compass, Azimuth . . . .141 
Compass, Boxing the ... 86 

Compass Card, 142 

Compass, Declination . . . 142 
Compass, Inclination . . . 142 
Compass, Mariners' . . . 142 
Compass, Points of the . . . 143 
Compass, Spirit .... 143 
Compass, Surveyors' . . . 143 
Compass, Variation of the . 32-558 

Compensating Coils, . . . 138 

Compensating Magnet, . . 336 

Compensating Poles, . . . 426 
Compensating Resistance, . . 144 
Complementary Distribution, . 144 

Complete Alternation, ... 23 

Component, 144 

Components of Earth's Magnetism, 356 
Composition of Forces, . . . 260 
Compound Arc, .... 39 
Compound, Binary . . . .81 
Compound, Chatterton's . . 116 



Page. 
Compound, Clark's .... 126 
Compound Dynamo, . . . 195 
Compounding, Over- . . . 399 
Compound Magnet, . . . 336 
Compound or Compound Wound 

Motor, 382 

Compound Winding, . . . 578 
Concentration of Ores, Magnetic 340 
Concentrator, Magnetic . . . 340 
Concentric Candle, ... 99 
Concentric Carbon, .... 107 
Condenser, ..... 144 
Condenser, Coatings of a, or Prime 

Conductor .... 129 
Condenser, Epinus' .... 242 
Condenser, Plate .... 417 
Condenser, Sliding .... 144 
Condenser, Varley's . . . 559 
Condensing Electroscope, . . 233 
Conductance, .... 144 
Conductance, Magnetic . . . 340 
Conduction, 144 

I Conduction, Electrolytic . . 215 

Conductive Discharge, . . 187 

i Conductivity, 144 

Conductivity, Magnetic . . 340 
Conductivity, Specific . . . 145 
Conductivity, Unit of . . . 145 
Conductivity, Variable . . . 145 

Conductor, 145 

Conductor, Anti-induction . . 145 
Conductor, Branch ... 87 
Conductor, Capacity of a Telegraph 103 
Conductor, Conical . . . 145 
Conductor, Imbricated . . . 146 
Conductor, Interpolar . . . 307 
Conductor, Leakage . . . 325 
Conductor, Prime . . 146-434 
Conductors, Equivalent . . . 146 
Conductors, Lamination of Arma- 
ture, 

Conductors, Service 
Conductor, Underground 
Congress Ohm, 
Congress Volt, . 
Conical Conductor, 
Conjugate, 

Connect, 

Connection, Cross 

Connection, Relay 

Connector, 

Consequent Points, 

Consequent Poles, 

Conservation of Electricity, 

Conservation of Energy, 

Constant Current, 

Constant Current Alternator, 

Constant Current Regulation 

Constant, Dielectric . 

Constant, Galvanometer 

Constant Potential, . 429 

Constant Potential Regulation, , 455 



319 
481 
552 
395 
568 
145 
146 
146 
158 
457 
146 
422 
146-478 
146 
239 
160 
24 
454 
183 



642 



INDEX. 



Page. 

. 541 

121-146 

. 147 



Constant, Time 

Contact Breaker, . . . 

Contact, Electric 

Contact Electricity, 

Contact Faults, 

Contact Key, Double . 

Contact Key, Sliding 

Contact Lamp, 

Contact, Line of 

Contact Point, 

Contact Potential Difference, 

Contact Ring, 

Contact Spring, 

Contact Series, 

Contact Theory, 

Continuity, Magnetic . 

Continuous Alternating Transformer 

547 
Continuous Current, . . .161 
Continuous Current Transformer, 

384-547 
Contraction, Anodic Closure, . . 36 
Contraction, Anodic Duration 
Contraction, Anodic Opening, 
Contraction, Kathodic Closure 
Contraction, Kathodic Duration 
Contractures, 
Contraplex Working, 
Control, Electro-magnetic 
Control, Gravity 
Controlled Clock, . 
Controlling Clock, . 
Controlling Field, . 
Controlling Force, 
Controlling Magnet, 
Control, Magnetic 
Control, Spring 
Convection, Electric 
Convection, Electrolytic 
Convection of Heat, Electric 
Convective Discharge, 
Conversion, Efficiency of 
Converter, .... 
Cooling Box, 
Co-ordinates, Origin of 
Co-ordinates, System of 
Copper, .... 
Copper Bath, 
Copper Stripping Bath, 
Copper Voltameter, . 
Cord Adjuster, 
Cord, Flexible . 
Cord, Pendant 
Core, .... 
Core, Armature 
Core, Cable 
Cored Carbon, 
Core-discs, 

Core-discs, Perforated . 
Core-discs, Pierced . 
Core-discs, Toothed 
Core, Laminated 



147 
147 
314 
316 
320 
330 
147 
147 
473 
148 
147 
148 
340 



36 

. 36 
. 312 

. 312 
. 148 

. 580 
. 218 

. 281 
. 127 

. 127 
. 148 

. 148 
185-336 

. 341 
. 492 

. 149 
149-214 

. 149 
. 187 

. 205 
. 149 

. 151 
. 397 

* 150 
. 151 

. 152 
. 152 

. 563 
. 152 

. 152 
. 405 

. 152 
43 



107 
152 
154 
152 
154 
154 



Page. 

Core, Magnet 336 

Core Ratio, 154 

Core, Ribbon 154 

Core, Ring 155 

Cores, Krizik's 318 

Core, Stranded .... 155 
Core, Tangentially Laminated . 155 
Core Transformer, . . . 155 

Core, Tubular 155 

Corpusants, 155 

Corresponding Points, . . . 422 

Coulomb, 155 

Coulomb's Law of Electrostatic At- 
traction and Repulsion, . . 155 
Coulomb's Law o f Magnetic Attrac- 
tion and Repulsion, . . 338 
Coulomb's Torsion Balance, . . 544 
Coulomb, Volt- . . . .568 
Counter, Electric . . . .156 
Counter Electro-motive Force, 156-228 
Counter-electro-motive Force Light- 
ning Arrester, .... 329 
Counter Inductive Effect, . . 204 

Couple, 156 

Couple, Astatic 157 

Couple, Axial .... 544 

Couple, Magnetic .... 341 
Couple, Moment of 544 

Couple, Thermo-electric . . . 532 
Couple, Voltaic or Galvanic . 156 

Coupling, 259 

Coupling of Dynamo, . . . 201 

C. P 157 

Crater 157 

Creep, Diffusion .... 184 

Creeping, 157 

Creeping, Magnetic .... 341 
Creeping of Magnetism, . . 356 

Crith, 157 

Critical Current, . . . .161 
Critical Distance of Alternative 

Path, 190 

Critical Resistance, .... 464 
Critical Speed, .... 157 
Critical Value, Villari's . . .561 
Crookes' Dark Space, . . . 489 

Cross, 157 

Cross-connecting Board, . . 157 
Cross Connection, .... 158 
Cross Induction, .... 298 

Crossing Cleat, 127 

Crossing Wires, . . . .158 
Cross-magnetizing Effect, . 158-298 
Cross-over Block, .... 158 

Cross, Peltier's 405 

Cross Talk 158 

Crucible, Electric . . . .158 
Crystallization, Electric . . 158 
Cube, Faraday's . . . .249 
Culture, Electro- . . . .209 
Cunynghame's Ammeter, . . 26 
Cup, Mercury .... 371 



INDEX. 



643 



Page. 

159-426 

159 



Cup, Porous 
Current, . 

Current, After 159 

Current, Alternating . . . 159 
Current, Alternating System . . 23 
Current, Alternative . . . 563 
Current Arc, Alternating . . 23 
Current, Atomic .... 160 
Current, Break Induced . . . 162 
Current, Charge .... 160 
Current, Circular . . . 160 

Current, Commuted . . . 160 

Current, Constant . . . 160 

Current, Continuous . . .161 
Current, Continuous, Transformer 384 
Current, Critical .... 161 

i Daniell Daniell 
Current, \ 161 

) U.S. or Siemens" Unit 
Current, Demarcation 
Current Density, . 
Current, Derived 
Current, Diacritical 
Current, Diaphragm 
Current, Direct 



Current, Direct Induced . 
Current, Direction of . 
Current, Displacement 
Current, Extra 
Current, Faradic 
Current, Field of Force of a 
Current, Foucault 
Current, Franklinic 
Current Generator, . 
Current, Induced . 
Current Induction, . 
Current Induction, Unipolar 
Current Intensity, . 
Current, Inverse Induced . 
Current, Jacobi's Unit of 
Current, Joint 
Current, Linear 
Current, Make and Break 
Current, Make Induced . 
Current Meter, . 
Current Meter, Alternating . 
Current, Negative . . . 

Current, Nerve and Muscle 
Current, Opposed 
Current, Partial 
Current, Polarizing 
Current, Positive 
Current, Power of Periodic 
Current, Pulsatory . 
Current, Rectified 
Current, Rectilinear 
Current, Redressed 
Current Regulation, Constant 
Current, Reverse Induced . 
Current Reverser, 
Currents, Ampere . 
Currents, Amperian 



161 

. 161 

. 164 

. 161 

. 161 

. 162 

. 162 

. 162 

. 162 

. 162 

. 162 

. 255 

. 163 

. 163 

. 277 

. 163 

. 163 

. 553 

. 163 

. 163 

. 163 

. 163 

. 164 

164-367 

. 163 

164-375 

. 373 

164 

, 164 

164 

164 

164 

164 

433 

164 

164 

165 

165 

454 

163 

165 

30 

165 



Page. 
Currents, Angular . . . 165 

Currents, Angular, Laws of . . 165 
Currents, Earth .... 166 
Current, Secondary .... 166 
Current, Secretion . . . 166 

Currents, Eddy .... 163 

Currents, Eddy Displacement . 162 
Currents in Parallel Circuits, Inde- • 

pend ence of ... . 297 
Current, Sinuous .... 166 
Current, Sheet .... 166 
Current, Shuttle . . . .483 
Currents, Local .... 163 
Currents, Local .... 331 

Currents, Multiphase . . . 166 
Currents, Natural . . . 166-389 
Currents, Nerve .... 390 
Currents of Motion, .... 167 
Currents of Rest, .... 167 
Currents, Orders of . . . . 167 
Currents, Parasitical . . . 163 
Currents, Polyphase . . . 167 

Currents, Rotatory . . . 167 
Currents, Thermo-electric . . 167 
Current Streamlets, . . . 495 
Current, Swelling .... 167 
Current, Tailing .... 501 
Current, Undulatory . . . 167 
Current, Unit .... 167 

Current, Wattless . . . .168 
Curve, Arrival .... 168 
Curve, Characteristic . . 113-168 
Curve, Characteristic, of Converter 169 
Curve, Charging .... 170 
Curve, Discharging . . . 170 

Curve, Elastic 206 

Curve, Electro-motive Force . 170 
Curve, External Characteristic . 171 
Curve, Harmonic . . . 174-485 
Curve, Horse Power . . .171 
Curve, Isochasmen . . . 171 

Curve, Life 171 

Curve, Load 172 

Curve, Magnetization . . . 172 
Curve of Distribution of Potential 

in Armature, . . . .172 
Curve of Dynamo, .... 173 
Curve of Saturation of Magnetic 

Circuit, 174 

Curve of Sines, . . . 173-485 
Curve of Torque, .... 174 
Curve, Permeability Temperature 174 
Curve, Sine .... 174-485 
Curve, Sinusoidal . . . 174-485 
Curves, Magnetic .... 341 

Cut In 174 

Cut Out, 174 

Cut Out, Automatic . . 175-475 
Cut Out, Magnetic . . . .175 
Cut Out, Plug .... 175 
Cut Out, Safety . . . .175 

Cut Out, Spring Jack . . .493 



644 



INDEX. 





Page. 




Page. 


Cut Outs, Time 


.541 


Deposit, Nodular . . 


. 392 


Cut Out, Wedge . 


. 175 


Depolarization, . 


. 180 


Cutting of Lines of Force, 


. 175 


Depolarizing Fluid, . 


. 258 


Cycle of Alternation, . 


. 175 


Derivation, Points of . 


180-423 


Cycle of Magnetization, . 


. 360 


Derivative Circuit, . 


. 123 


Cylinder, Armature 


43 


Derived Circuit, 


. 123 


Cylinder, Electric Machine 


. 333 


Derived Current, 


. 164 


Cylindrical Armature, . 


. • 45 


Derived Units, 


. 555 


Cystoscopy, .... 


. 175 


Desk Push, .... 


. 180 






Detector, .... 


. 180 


Damper, ..... 


. 176 


Detector, Lineman's 


. 180 


Damping, .... 


. 176 


Deviation of Discharge, 


. 188 


Damping Magnet, 


. 336 


Deviation, Quadrantal 


. 180 


Daniell's Standard Voltaic Cell, 


109 


Deviation, Semi-circular 


. 181 


Dark Space, Faraday's 


. 249 


Device, Safety .... 


. 475 


D'Arsonval's Battery, . 


62 


Dextrotorsal, .... 


. 181 


Dash-pot, . . . . 


. 176 


Diacritical, .... 


. 181 


Dead Beat, .... 


38-176 


Diacritical Current, 


. 161 


Dead Beat Discharge, 


. 187 


Diagometer, .... 


. 181 


Dead Earth, .... 


176-203 


Diagnosis, Electro- 


181-210 


Dead Point of an Alternator, . 


. 177 


Diagram, Thermo-electric 


. 532 


Dead Turns, .... 


. 177 


Dial Telegraph, 


. 505 


Dead Turns of a Dynamo, 


. 551 


Diamagnetic, .... 


. 181 


Dead Wire, .... 


. 177 


Diamagnetic Polarity, . 


181-423 


Death, Electrical 


. 177 


Diamagnetism, .... 


. 182 


Debrun Candle, • 




Diameter of Commutation, . 


. 182 


Decalescence, .... 


. 177 


Diapason, Electric , 


. 182 


Decay of Magnetism, . 


. 356 


Diaphragm, .... 


. 182 


Deci, 


. 177 


Diaphragm Current, 


. 161 






Dielectric, .... 


. 182 


Declination, Angle of 




Dielectric Capacity, . 


. 102 






Dielectric Constant, 


. 183 


Declination, Magnetic 




Dielectric, Energy of 


. 183 


Declination Map, . 


. 309 


Dielectric Polarization, 


. 183 


Declination of the Magnetic Needle, 17! 


Dielectric Resistance, 


183-464 


Decomposition, 


. 178 


Dielectric Strain, 


. 183 


Decomposition, Electrolytic . 


. 178 


Dielectric Strength, 


. 183 


Decrement, .... 


. 178 


Dielectric Stress, 


. 496 


De-energize, .... 


. 178 


Differential Arc Lamp, 


. 320 


Deflagration, . . 


. 178 


Differential Coil and Plunger, 


. 132 


Deflagrator, Hare's . 


. 73 


Differential Galvanometer, . 


. 268 




. 178 


Differentially Wound Bell, 


. 79 


Deflection, 


. 178 


Differential Magnetometer, 


. 365 


Deflection Method, 


. 178 


Differential Motor, . 


. 382 


Deflection of Magnet, 


. 337 


Differential Relay, 


. 457 


Degeneration, Reaction of . 


. 179 


Differential Thermo-electric Pile, 533 


Degradation of Energy, . 


. 239 


Differential Winding Working, 


. 183 


Deka 


. 179 


Diffusion, 


. 184 


De la Rive's Floating Battery, 


. 179 


Diffusion, Anodal . 


35 


De la Rue Batterv, 


62 


Diffusion Creep, 


. 184 


Delaurier's Solution, 


. 179 


Digney Unit of Resistance, 


. 464 


Delezenne's Circle, 


. 133 


Dimensions and Theory of Dimen- 


Demarcation Current, 


. 161 


sions, .... 


. 184 


Demagnetization, . 


. 179 


Dimmer, 


. 185 


Density, Current 


. 161 


Diode Working, 


. 580 


Density, Electrical 


. 115 


Dioxide, Carbon 


. 107 


Density, Electric Superficial . 


. 180 


Dioxide, Sulphur . 


. 497 


Density, Field 


. 252 


Dip, Magnetic .... 


342-346 


Density, Magnetic . . . 


. 342 


Dip of Magnetic Needle, 


. 185 


Density of Charge, 


115-180 


Dipping, 


. 185 


Dental Mallet, Electric . 


. 180 


Dipping Needle, 


. 185 


Deposit, Electrolytic 


. 180 


Direct Current, 


. 162 



INDEX, 



645 



Direct Current Dynamo, 
Direct Induced Current, . 
Direct Reading Galvanometer 
Directing Magnet, . 
Direction, 

Direction of Current 
Direction, Positive 
Directive Power, 
Disc, Arago's 
Disc, Armature . 
Disc, Bunsen . 
Disc, Dynamo . 
Disc, Faraday's 
Discharge and Charge Key, 
Discharge, Brush . 
Discharge, Conductive 
Discharge, Convective 
Discharge, Dead Beat 
Discharge, Disruptive 
Discharge, Duration of 
Discharge, Glow . 
Discharge, Impulsive 
Discharge Key, Kempe's 
Discharge, Lateral . 
Discharge of Magnet sm, 
Discharge, Oscillatory 
Discharger, 

Discharger, Henley's U 
Discharger, Universal 
Discharger, Universal 
Discharge, Silent . 
Discharge, Spark 
Discharge, Surging 
Discharging Curve, . 
Discharging Rod, . 
Discharging Tongs, 
Disconnection, 
Discontinuity, Magnetic 
Discovery, Oerstedt's 
Disc Winding, . 
Dispersion Photometer, 
Displacement Current, 
Displacement, Electric 
Displacement, Oscillatory 
Disruptive Discharge 
Disruptive Tension, 
Dissimulated Electricity 
Dissipation of Charge, 
Dissociation, . 
Distance, Critical, of 

Path 
Distance, Explosive 
Distance, Sparking 
Distance, Striking 
Distant Station, 
Distillation, 
Distortion of Field, 
Distributing Box, 
Distributing Switches, 
Distribution, Complementary 
Distribution, Isolated 
Distribution of Charge, , 



niversal 

Henley's 

18? 



1ST 
139 
139 
115 
139-535 
Alternative 

190 

, 190 
190 

, 496 
493 

, 190 
252 
190 
190 
144 
309 
115 



Page. 

197 
. 162 

269 
. 185 

185 
. 182 

428 
. 187 



4-3 
92 
197 
•J49 
313 
1ST 
1ST 
137 
187 
187 
138 
137 
188 
315 
1SS 
336 
188 
188 
189 
189 
189 
189-206 
. 189 
188 
170 
189 



139 
342 

394 
579 
412 

162 
188 



Page. 
Distribution of Electric Energy, 

Systems of .... 190 
Distribution of Magnetism, Lamel- 
lar, 357 

Distribution of Magnetism, Solen- 

oidal 358 

Distribution of Supply, Central Sta- 
tion .112 

Door Opener, Electric . . 190 

Dosage, Galvanic .... 190 
Double Break Switch, . • . 500 

Double Carbon Arc Lamp, . . 191 
Double Contact Ke\ , . . 314 

Double Curb Working, . . .581 
Douole Fluid Theory, . . 191 

Double Fluid Voltaic Cell, . . 191 
Double Magnetic Circuit, . . 340 
Double Needle Telegraph, . . 506 
Double Plug, . . . .191 

Double Pole Switch, . . .500 

Double Tapper Key, . . . 314 
Double Touch, Magnetization by . 358 
Double Trolley, . . . .549 

Double Wedge 191 

Doubler, 191 

D. P., 191 

Drag, 191 

Drag of Field, 254 

Dreh-Strom, .... 191 

Drill, Electric . . . .191 

Drip Loop, 192 

Driving Horns, .... 192 

Dronier's Salt, .... 192 
Drooping Characteristic, . . 114 

Drop, Annunciator ... 35 
Drop, Automatic ... . . 192 
Drop, Calling 
Drum Armature, 
Drum, Electric 

Dry Battery 

Dry Pile, Zamboni's 

Dub's Laws, .... 

Duct, 

Duplex Bridge Telegraph, 

Duplex Cable, 

Duplex Differential Telegraph, 

Duplex Telegraph, 

Duration Contraction, Kathodic 

Duration of Electric Spark, 

Dyad 

Dyeing, Electric 
Dynamic Electricity, 
Dynamic, Electro- 
Dynamic Induction, Magnetic 
Dynamo, Alternating Current 
Dynamo, Alternating Current, Re : 
ulation of .... 

Dynamos, Battery of ... 68 
Dynamo, Commercial Efficiency 

of 195 

Dynamo, Compound . . . 195 
Dynamo, Coupling of 201 



646 



INDEX. 



Page. 
Dynamo, Curve of 173 

Dvnamo, Dead Turns of a . .551 
Dynamo, Direct Current . .197 

Dynamo, Disc 197 

Dynamo-electric Machine, . . 197 
Dynamo, Electroplating . . .198 
Dvnamo, Equalizing . . 198 
Dynamo, Field and Armature Re- 
action of 450 

Dynamo, Far Leading . . . 198 
Dynamo or Magneto-electric Gen- 
erator, Flashing in a . . 257 
Dynamo, Inductor . . . 199 
Dynamo, Interior Pole . . . 199 
Dynamo, Iron Clad . . . 200 
Dynamo, Ironwork Fault of a . 308 
Dynamo, Motor .... 200 
Dynamo, Multipolar . . .200 
Dynamo, Non-polar . . . 200 
DynamOj Open Coil . . . .200 
Dynamo, Overtype . . . 399 
Dynamos, Regulation of . . . 455 
Dynamo, Ring .... 200 
Dynamo, Self Exciting . . .201 
Dynamo, Separate Circuit . . 201 
Dynamo, Separately Excited 201-479 
Dynamo, Series .... 201 
Dynamo, Shunt .... 202 
Dynamo, Single Coil . . . 202 
Dynamo, Tuning Fork . . . 202 
Dynamo, Unipolar . 202-553 
Dynamograph, .... 199 
Dynamometer, .... 200 
Dyne, 203 

Earth, 203 

Earth Coil 133 

Earth Currents, . . . .166 
Earth, Dead . . . . 176-203 
Earth, Magnetization by . . 359 
Earth, Partial .... 203-404 
Earth Plate, ... . . .203 

Earth Return, 203 

Earth's Magnetism, Components 

of 356 

Earth, Solid 203 

Earth, Swinging . . . .203 
Earth, Total . . • . .203 

Ebonite, 203 

Eccentric Iron Disc Ammeter, . 27 
Economic Coefficient, . 130-204-205 
Eddy Currents, .... 163 
Eddy Displacement Currents, . 182 

Ediswan, 204 

Edison Effect 204 

Edison-Lalande Battery, . . 69 
Eel, Electric . . . . .204 
Effect, Acheson . . . .208 
Effect, Counter-inductive . . ^04 
Effect, Cross-magnetizing . 158-298 

Effect, Edison 204 

Effect, Faraday .... 249 



Page. 
Effect, Ferranti . . . .251 

Effect, Hall 284 

Effect, Joule 311 

Effect, Kerr .... 235-312 
Effect, Mordey . . . . .381 



Effect, Page . 


. 401 


Effect, Peltier . 


. 404 


Effect, Photo-voltaic 


. 415 


Effect, Seebeck . 


. 478 


Effect, Skin . 


. 486 


Effect, Thomson 


. 538 


Effect, Voltaic 


. 563 


Efficiency, .... 


.204 


Efficiency, Commercial 


. 204 


Efficiency, Electrical 


. 205 


Efficiency, Gross . 


. 205 


Efficiency, Intrinsic . 


. 205 


Efficiency, Net 


. 205 


Efficiency of Conversion, 


. 205 


Efficiency of Secondary Battery, 


Quantity 


. 205 


Efficiency of Secondary Battery, 


Real .... 


. . 205 


Efflorescence, 


. 206 


Effluvium, Electric . 


. 206 


Egg, Philosopher's 


. 409 


Elastic Curve, . 


. 206 


Elasticity, Electric 


. 206 


Electrepeter, 


. 206 


Electric, Absolute, Potentia 


. 429 


Biectric Absorption, 


. 8 


Electric Actinometer, . 


11 


Electric Alarm, . 


. 17 


Electrical Classification of Ele- 


ments 


. 237 


Electrically Controlled Valve, . 558 


Electric Ammunition Hoist, 


. 29 


Electric Analysis, . 


32 


Electric Analyzer, 


. 32 


Electric Annealing, 


34 


Electric Annunciator Clock, 


. 127 


Electric Arc Blow-pipe, 


84 


Electric Aura, . 


. 53 


Electric Automatic Fire 


Extin- 


guisher, 


. 257 


Electric Axis, 


.« 54 


Electric Balance, 


. 577 


Electric Bath, Bipolar . 


. 57 


Electric Bath, Multipolar 


. 57 


Electric Bath, Unipolar 


57 


Electric Bell, 


. 79 


Electric Bell, Automatic 


78 


Electric Bioscopy, 


. 82 


Electric Blasting, . 


83 


Electric Bleaching, . 


. 83 


Electric Boat, 


84 


Electric Boiler Feed, 


. 84 


Electric Branding, 


87 


Electric Brazing, 


. 87 


Electric Breath Figures, 


89 


Electric Breeze, 


. 89 


Electric Buoy, 


93 





INDEX. 


647 




Page. 




Page. 


Electric Candle, 


. 99 


Electricity, Atmospheric . 


, V .51 


Electric Case Hardening, 


. 109 


Electricity, Cal . _ . 


. 208 


Electric Cautery, 


. 109 


Electricity, Conservation of . . 146 


Electric Chimes, 


. 118 


Electricity, Contact 


. » . 147 


Electric Chronograph, 


. 118 


Electricity, Dissimulated 


. 189 


Electric Circuit, Active 


. 123 


Electricity, Dynamic 


. 193 


Electric Clock, Self-winding 


. 128 


Electricity, Frictional 


. 262 


Electric Coil, .... 


. 133 


Electricity, Latent 


. 323 


Electric Column, 


. 139 


Electricitv, Negative 


. 389 


Electric Contact, . 


. 147 


Electricity, Plant 


. 317 


Electric Convection, 


. 149 


Electricity, Positive 


. 428 


Electric Convection of Heat, 


143-286 


Electricity, Specific Heat of . 491 


Electric Counter, 


. 156 


Electricity, Static 


. 493 


Electric Crucible, . 


. 158 


Electricity, Storage of 


. 495 


Electric Crystallization, . 


. 158 


Electricity, Voltaic 


. 563 


Electric Death, 


. 177 


Electricity, Vitreous 


. 562 


Electric Density, 


. 115 


Electric Machine, Plate 


. 417 


Electric Dental Mallet, 


180 


Electric Machine, Wimshurst . 577 


Electric Diapason, 


. 182 


Electric Mains, 


. 367 


Electric Displacement, . 


189 


Electric Mass, . 


. 368 


Electric Door Opener, 


. 190 


Electric Matter, . 


. 368 


Electric Double Refraction, 


. 454 


Electric Meter, Chemical 


. 375 


Electric Drill, . 


. 191 


Electric Meter, Thermal 


. 375 


Electric Drum, 


. 193 


Electric Meter, Time 


. 375 


Electric Dyeing, 


. 193 


Electric Mortar, 


. 382 


Electric Eel, .... 


. 204 


Electric Motor, 


. 382 


Electric Efficiency, . 


. 205 


Electric or Electrostatic Capacity 102 


Electric Effluvium, 


. 206 


Electric Organ, 


. 397 


Electric Elasticity, . 


. 206 


Electric Oscillations, 


. 398 


Electric Endosmose, 


. 238 


Electric Osmose, 


. 338 


Electric Energy, 


. 239 


Electric Pen, 


. 405 


Electric Energy, Coefficient of 


. 205 


Electric Pendulum, 


. 405 


Electric Energy, Systems of 


Dis- 


Electric Piano, 


. 415 


tribution of 


. 190 


Electric Picture, 


. 415 


Electric Engraving, . 


. 245 


Electric Pistol, 


. 416 


Electric Entropy, . 


. 242 


Electric Popgun, 


. 282 


Electric Etching, 


. 245 


Electric Portrait, . 


. 415 


Electric Evaporation, . 


. 246 


Electric Potential Difference, . 429 


Electric Excitability cf Ar 


limal 


Electric Potential, Unit of 


. 432 


Systems, .... 


. 247 


Electric Power, 


. 433 


Electric Exosmose, . 


. 247 


Electric Pressure, 


. 434 


Electric Expansion, 


. 247 


Electric Probe, 


. 435 


Electric Fire Alarm, Automati 


c, . 257 


Electric Prostration, 


. 437 


Electric Floor Matting, 


. 369 


Electric Protector, . 


. 437 


Electric Fluid, . 


. 258 


Electric Radiometer, . 


. 44T 


Electric Fly or Flyer, . 


. 259 


Electric Ray, 


. 450 


Electric Fog, . 


. 259 


Electric Rectification of Alcohol, 


Electric Furnace, . 


. 263 


Electric Reduction of Ores 


. 453 


Electric Fuse, . . . . 


. 264 


Electric Reduction of Phosphorous 410 


Electric Gas Burners, . 


93 


Electric Register, 


. 454 


Electric Headlight, . 


. 285 


Electric Residue, 


. 116-460 


Electric Head Bath, 


. 284 


Electricity, Resinous . 


. 461 


Electric Heat, . 


. 285 


Electric Resonance, 


. 468 


Electric Heater, 


. 286 


Electric Resonator, 


. 470 


Electric Horse Power, 


. 290 


Electric Rings, 


. 392 


Electric Image, 


. 296 


Electrics, 


. 208 


Electric Incandescence, . 


. 297 


Electric Saw, 


. 476 


Electric Influence, 


. 305 


Electric Screen, 


. 476 


Electric Insulation, . 


. 305 


Electric Shadow, 


. 480 


Electricities, Separation of . 


. 479 


Electric Shock, 


. 482 


Electricity, . 


. 206 


Electric Shower Bath, 


. 57 


Electricity, Animal 


33 


Electric Soldering, 


. 487 



648 



INDEX. 



Page. 
Electric Spark, Duration of . . 490 
Electric Sphygmophone, . . 491 
Electric Storms, . . . . 495 
Electric Striae, 
Electric Subway, . ' . . . 496 
Electric Subway, Underground . 552 
Electric Sunstroke, .... 497 
Electric Superficial Density, . 180 
Electric Swaging, .... 499 
Electric Tele-barometer, . . 504 
Electric Telemanometer, . . 521 

Electric Telemeter, . . .521 
Electric Tempering, . . . 527 

Electric Tension, . . . .529 
Electric Thermometer, . . . 535 
Electric Thermostat, . . .537 
Electric Torpedo, . . . .543 
Electric Tower, .... 545 
Electric Transmission of Energy, . 240 
Electric Trumpet, .... 550 
Electric Tube, . . . . . 550 
Electric Typewriter, . . . 551 
Electric Unit of Work, . . .580 
Electric Varnish, .... 559 
Electric Welding, . . . .574 

Electric Whirl 577 

Electric Wood, . . . .578 

Electrification, .... 208 

Electrification by Cleavage, . . 127 

Electrification by Pressure, . 434 

Electrified Body, Energy of an . 241 

Electrization, 

Electro-biology, 

Electro-capillarity, 

Electro-chemical Equivalents, 

Electro-chemical Series, 

Electro-chemistry, . 

Electro-culture, 

Electrode, .... 

Electrode, Indifferent 

Electrodes, Erb's Standard of 

Electrodes, Non-polarizable 

Electrodes, Shovel . 

Electrode, Therapeutic 

Electro-diagnosis, 

Electro-dynamic, . 

Electro-dynamic Attraction 

Repulsion, 
Electro-dynamic Rotation of Liq 

uids, .... 

Electro-dynamometer, Siemens 
Electro-gilding, 
Electro-kinetic, 
Electrolier, 

Electrolysis, .... 
Electrolysis, Laws of . 
Electrolyte, .... 
Electrolytic Analysis, . 
Electrolytic Cell, 
Electrolytic Clock, 
Electrolytic Conduction, 



Electrolytic Convection, 



. 208 
^09 

209-244 
209 
209 
209 
210 
210 
210 
210 
483 
210 

181-210 
211 
and 

211 

474 

212 
277 
211 
212 
212 
213 
214 
214 
109 
128 
215 



Page. 

. 180 
. 308 

. 464 
215-3 7 

. 16 
. 217 

. 217 
. 217 

. 291 



Electrolytic Deposit, 
Electrolytic Iron, 
Electrolytic Resistance, 
Electro-magnet, 
Electro-magnet, Annular 
Electro-magnet, Bar 
Electro-magnet, Club-foot 
Electro-magnet, Hinged 
Electro-magnet, Hughes' . . 291 
Electro-magnetic Ammeter, . 27 

Electro-magnetic and Magnetic 

Equipotential Surface, . 
Electro-magnetic Attraction and 

Repulsion, 
Electro-magnetic Brake, 
Electro-magnetic Clutch, 
Electro-magnetic Control, . 
Electro-magnetic Eye, 
Electro-magnetic Field of Force 
Electro-magnetic Force, . 
Electro-magnetic Gun, 
Electro-magnetic Induction 
Electro-magnetic Inertia . . 305 
Electro-magnetic Induction, Mutual 302 
Electro-magnetic Interrupter for 



244 

'. 217 

86 

. 128 

218 
. 248 

218 
. 260 



218-299 
305 



149-214 



Tuning Fork, 
Electro-magnetic Leakage 



307 
219 
219 



Electro-magnetic Leakage, 

Electro-magnetic Lines of Force, . 219 

Electro-magnetic Liquids, Rotation 
of 475 

Electro-magnetic Meter, 

Electro-magnetic Quantity, . 

Electro-magnetic Quantity, Prac- 
tical Unit of .... 445 

Electro-magnetic Shunt, . . 483 

Electro-magnetic Stress, . 219-496 

Electro-magnetic Theory of Light, 219 

Electro-magnetic Unit of Energy, 220 

Electro-magnetic Vibrator, 

Electro-magnetic Waves, 

Electro-magnet, Ironclad 

Electro-magnetism, . 

Electro-magnet, Joule's 

Electro-magnet, Long Range 

Electro-magnet, One Coil, . 

Electro-magnet, Plunger, 

Electro-magnet, Polarized . 

Electro-magnets, Interlocking 

Electro-magnets, Multiple 
Method of Working . 

Electro-magnet, Stopped Coil, 

Electro-magnets, Surgical 

Electro-mechanical Bell, 

Electro-mechanical Equivalent. 

Electro-medical Baths, 

Electro-medical Battery, Pulver- 
macher's .... 

Electro-metallurgy, 

Electrometer, . • . 

Electrometer, Absolute . 

Electrometer, Attracted Disc 

Electrometer, Capillary , 



375 
445 



561 
. 573 

219 
. 220 

337 
. 220 

219 
. 220 

220 
. 221 
Wire 

. 388 

221 

. 222 

80 

. 244 

222 



222 
222 
222 
223 

224 



INDEX. 



649 



Electrometer Gauge, . . .226 
Electrometer, Lane's . . . 226 
Electrometer, Quadrant . . 226 
Electrometer, Thermo- . . . 536 
Electrometer, Weight . . . 223 
Electro-motive Force, . . . 227 
Electro-motive Force, Counter- . 228 
Electro-motive Force Curve, . . 170 
Electro-motive Force, Impressed 297 
Electro-motive Force, Motor . . 384 
Electro-motive Force, Oscillatory 398 
Electro-motive Force, Transverse 549 
Electro-motive Force, Unit . 228 

Electro-motive Intensity, . . 228 

Electro-motivePotential Difference, 429 
Electro-motive Series, . . . 228 
Electro-motograph, . . . 229 

Electro-motor, 229 

Electro-muscular Excitation, . 229 
Electro-negative, .... 229 
Electro-optics, .... 229 
Electrophone Action, . . , 230 
Eloetrophorus, .... 230 
Electro-physiology, .... 231 
Electroplating, . . . 231-418 
Electroplating Dynamo, . . . 198 
Electro-pneumatic Signals, . . 231 
Electropoion Fluid, . . . .232 
Electro-positive, .... 232 
Electro-puncture, .... 232 
Electro-receptive, .... 232 

Electroscope, 232 

Electroscope, Bennett's . . 233 
Electroscope, Bohenberger's . . 233 
Electroscope, Condensing . . 233 
Electroscope, Gold Leaf . . 233 
Electroscope, Pith Ball . . 234 
Electrostatic Attraction and Repul- 
sion, 234 

Electrostatic Attraction and Repul- 
sion, Coulomb's Law of . 155 
Electrostatic Circuit, . . . 123 
Electrostatic Equipotential Surface, 244 
Electrostatic Field of Force, . . 254 
Electrostatic Force, . . . 260 
Electrostatic Induction, . . . 302 
Electrostatic Induction, Coefficient 
of 234 



Electrostatic Induction, Mutual 303 
Electrostatic Lines of Force, . . 234 
Electrostatic Quantity, . . 445 
Electrostatic Refraction, . . 235 
Electrostatics, . . . .235 
Electrostatic Series, \ 235 

Electrostatic Stress, . . 236-496 
Electrostatic Telephone, . . . 526 
Electrostatic Voltmeter, . . 571 
Electro-thermal Equivalent, . . 245 
Electro-therapeutics or Therapy, 236 
Electrotonic State, .... 493 
Electrotonus, .... 236 
Electrotype, 236 



Page. 
Element, Chemical . . . .236 
Element, Galvanic . . . 264 

Element, Mathematical . . . 237 
Element, Negative ... 390 
Element of a Battery Cell, . . 237 
Element, Positive .... 277 
Elements, Electrical Classification 

of . 237 

Elements, Magnetic . . . 342 
Elements of Battery, . . .63 
Elements, Thermo-electric . . 237 
Element, Voltaic . . . .237 
Elias' Method of Magnetization, 360 
Elongation, .... 237-540 
Elongation, Magnetic . . . 344 
Embosser, Telegraph . . . 237 

E. M. D. P., 238 

E. M. F M 238 

Energy, 238 

Energy, Atomic .... 238 

Energy, Chemical .... 239 
Energy, Conservation of . . 239 

Energy, Degradation of . . 239 
Energy, Electric . . . .239 
Energy, Electrical, Coefficient of 205 
Energy, Electric Transmission of . 240 
Energy, Electro-magnetic, Unit of 220 
Energy, Kinetic .... 241 
Energy, Mechanical . . . 241 

Energy Meter, .... 375 

Energy, Molar 241 

Energy, Molecular . . . 241 
Energy of an Electrified Body, . 241 
Energy of Dielectric, . . . 183 
Energy of Position, .... 241 
Energy of Stress, .... 241 
Energy, Physical . . . .241 
Energy, Potential, or Static . 241 

Energy, Radiant .... 446 
Energy, Thermal .... 242 
End-on Method, .... 238 
End or Pole, Marked, . . .368 
Endosmose, Electric . . . 238 

End Play 238 

End, Unmarked .... 556 
English Absolute or Foot Second 

Unit of Resistance, . . . 465 
Engraving, Electric . . . 245 

Entropy, 242 

Entropy, Electric . . . . 242 
Epinus' Condenser, .... 242 

E. P. S., 243 

Equator, Magnetic .... 344 
Equator of Magnet . . 337 

Equipotential, . . . . ' . 244 
Equipotential Surface, . . 498 

Equipotential Surface, Electrostatic 244 
Equipotential Surface, Magnetic 

and Electro-magnetic . . 244 

Equalizer, 243 

Equalizer, Feeder . . . .251 
Equalizing Dynamo, . . . 198 



650 



INDEX. 



Page. 
Equivalent, Chemical . . 116-244 
Equivalent Conductors, . . 146 
Equivalent, Electro-thermal . . 245 
Equivalent, Joule's . . . 311 
Equivalent Resistance, . . . 465 
Equivalents, Electro-chemical 209-244 
Equivalent, Thermo-chemical . 245 

Equivalent, Water . . . 572 

Equivolt, 245 

Erb's Standard of Electrodes, . 210 

Erg, 245 

Erg-ten, 245 

Error, Heating 286 

Escape, 245 

Essential Resistance, . . 465-466 
Etching, Electric . . .245 

Ethene, 397 

Ether, 246 

Eudiometer, 246 

Evaporation, Electric . . . 246 
Ewing's Theory of Magnetism, . 356 
Exchange, Telephone . . . 246 
Excitation, Electro muscular . 2i9 

Excitability, Faradic . . .246 
Excitability, Galvanic . . . 247 
Excitability of Animal System, 

Electric 247 

Exciter, .... .247 

Exosmose, Electric .... 247 
Expansion, Coefficient of . . 247 
Expansion, Electric .... 247 
Experiment, Franklin's . . 261 
Experiment, Hall's . . . .284 
Experiment, Kerr's . . .312 
Experiment, Matteueci's . . . 369 
Experiments, Hertz's . . . 470 
Experiment, Volta's Fundamental 567 
Experiment with Frog, Galvani's 262 

Exploder, 247 

Explorer, 247 

Exploring Coil, . . . .350 

Explosive Distance, . . . 190 
Extension Bell Call, . . . .248 
Extension, Polar .... 423 
External Characteristic . . .114 
External Characteristic Curve, . 171 
External Circuit, . . . .123 
External Resistance, . . 465-467 
Extinguisher, Automatic Electric 

Fire ...*.. 257 
Extra Current, .... 162 
Extra-polar Region, . . . 454 
Eye, Electro-magnetic . . . 248 
Eye, Selenium 478 

Facsimile Telegraph, . . . 510 

Factor, Armature . . . .45 

Fahrenheit Scale 248 

Fall of Potential, . . . .430 

False Poles, Magnetic . . 350 

Farad, 248 

Faraday, Effect .... 249 





Page. 


Faraday's Cube, 


. 249 


Faraday's Dark Space, 


249-489 


Faraday's Disc, 


. 249 


Faraday's Net, 


. 250 


Faraday's Ring, 


. 473 


Faraday's Transformer, 


. 250 


Faraday's Voltameter, 


. 250 


Faradic, 


. 250 


Faradic Battery, 


. 63 


Faradic Brush, 


. 251 


Faradic Current, 


. 162 


Faradic Excitability, 


. 246 


Faradization, .... 


. 251 


Faradization, Galvano- 


. 265 


Far Leading Dynamo, 


. 198 


Fault of a Dynamo, Ironwork 


. 308 


Faults, 


. 251 


Faults, Contact 


. 147 


Feed Clockwork, 


. 128 


Feeder, 


. 251 


Feeder, Equalizer 


. 251 


Feeder, Main or Standard . 


. 251 


Feeder, Negative 


. 251 


Feeder, Neutral 


. 251 


Feeder, Positive 


. 251 


Feeder, Switch 


. 500 


Feet, Ampere .... 


. 30 


Ferranti Effect, 


. 251 


Ferric Chloride Battery, 


. 63 


Ferro-magnetic, 


252 


Fibre and Spring Suspension, 


. 252 


Fibre Suspension, 


252 


Field, Air 


. 252 


Field, Alternating 


252 


Field and Armature Reaction 


of 


Dynamo, .... 


450 


Field, Controlling 


. 148 


Field, Deflecting . 


178 


Field Density, .... 


. 252 


Field, Distortion of 


252 


Field, Drag of . 


. 254 


Field, Intensity of a Magnetic 


306 


Field Magnet, .... 


. 337 


Field of Force, 


254 


Field of Force, Electro-magnetic 


. 218 


Field of Force, Electrostatic 


254 


Field of Force, Magnetic 


. 344 


Field of Force of a Current, 


255 


Field of Force, Uniform . 


. 553 


Field, Pulsatory . . . . 


256 


Field, Rotating 


. 256 


Field, Stray S 


>56-495 


Field, Uniform .... 


. 256 


Field, Uniform Magnetic 


345 


Field, Waste .... 


. 256 


Figure of Merit, 


. 256 


Figures, Haldat's 


284 


Figures, Lichtenberg's . 


. 327 


Figures, Magnetic 


345 


Filament 


. 256 


Filament, Magnetic 


345 


Filaments, Paper 


. 402 



INDEX. 



6.SI 



File, Circuit Breaker . .121 

Finder, Position .... 427 
Finder, Range .... 447 

Finder, Wire 580 

Fire Alarm, Electric Automatic . 257 
Fire and Heat Alarm, . . .17 
Fire Extinguisher, Electric Auto- 
matic 257 

Fire Cleansing, .... 257 
Fire, St. Elmo's . . . .494 

Fishmg Box, 311 

Flashing in a Dynamo or Magneto- 
Electric Generator, . . . 257 
Flashing of Incandescent Lamp 

Carbons, . . . . .257 
Flashing Over, .... 258 

Flash, Side 484 

Flat Cable, 96 

Flat Coil, ...... 133 

Flat Ring Armature, ... 45 

Flats, 258 

Flats in Commutator, . . . 140 

Flexible Cord, 152 

Floating Battery. De la Rive's . 179 
Floating Magnets, Meyer's . . 370 
Floor Matting, Electric . . 369 
Floor Push, . . . .258 

Fluid, Depolarizing . . .258 

Fluid, Electric 258 

Fluid, Electropoion . . . 232 
Fluid, Insulator .... 306 

Fluid, North Magnetic . . 357 

Fluids, Magnetic .... 345 
Fluid, South Magnetic . . . 356 
Fluid Theory, Single . . .486 
Fluorescence, .... 258 

Flush Boxes 258 

Fluviograph, .... 259 

Flux, Magnetic .... 345 

Fly or Flyer, Electric . . . 259 

Foci Magnetic, 259 

Fog, Electric 259 

Following Horns, .... 259 

Foot-candle, 259 

Foot, MiK 379 

Foot-pound, 259 

Foot-step 259 

Force 259 

Force, Angular 544 

Force, Axial 544 

Force, Centrifugal . . .112 

Force, Coercive or Coercitive 131-471 
Force, Controlling . . .148 

Force, Counter-electro-motive . 156 
Force de Cheval, .... 260 
Force, Electro-magnetic . . . 260 
Force, Electro-motive . . 227 

Force, Electro-motive, Transverse 549 
Force, Electrostatic . . . 260 

Force, Field of 254 

Force, Field of, of a Current . 255 
Force, Field of, Electrostatic . . 254 



Force, Kapp Line of 

Force, Lines of 

Force, Magnetic 

Force, Magnetic Field of 

Force, Magnetic Lines of 

Force, Magneto-motive . 

Force, Motor Electro-motive 



312 
. 330 
346 
. 344 
348 
. 365 
384 
Force of Polarization, Back Elec- 
tro-motive 156 

Force, Oscillatory, Electro-motive 398 
Force, Photo-electro-motive . . 410 
Forces, Composition of . . 260 



Forces, Parallelogram of 

Forces, Resolution of . 

Force, True Contact 

Force, Tubes of 

Force, Unit of . 

Forked Circuits, 

Fork, Tuning, Dynamo . 

Forming, 

Formula of Merit, 

Foucault Current, . 

Foundation Ring, 

Fourth State of Matter, 

Frame, ... 

Frame, Resistance 

Franklinic Current, . 

Franklin's Experiment, 

Franklin's Plate, 

Franklin's Theory, 

Free Charge, 

Free Magnetism, . 

Frequency, 

Frequency, High . 

Frictional Electricity, 

Frictional Electric Machine 

Frictional Heating, . 

Friction Gear, Magnetic 

Friction, Magnetic . 

Fringe, .... 

Frog, Galvani's Experiment 

Frog, Rheoscopic . 

Frying, 

Fulgurite, 

Fuller's Battery, 

Fulminating Pane, 

Fundamental Unit, . 

Furnace, Electric . 

Fuse Block, 

Fuse Board, . 

Fuse Box, . 

Fuse, Cockburn 

Fuse, Electric . 

Fuse Links, . 

Fuse, Safety 



Galvanic, 

Galvanic Action, Volta's Law of 

Galvanic Dosage, . 

Galvanic Element, . 

Galvanic Excitability, . 

Galvanic or Voltaic Battery 



with 



. 260 
261 

. 549 
261 

. 261 
126 

. 202 
261 

. 256 
163 

. 261 
261 

. 261 
465 

. 163 
261 

. 262 
262-486 

. 115 
356 
262 
289 
262 
333 
262 
276 
295-346 
262 



262 
263 
263 
63 
262 
554 
263 
175 



263 
. 264 

330 
"5-475 

264 

. 568 
190 

. 264 
247 



652 



INDEX. 



Galvanic or Voltaic Circle, 
Galvanic or Voltaic Couple 
Galvanic Polarization, . 
Galvani's Experiment with Frog 
Galvanism, 
Galvanization, . 
Galvanization, Labile 
Galvanized Iron, 
Galvano-cautery, . 
Galvano-cautery, Chemical 
Galvano-electric Cautery, 
Galvano-faradization, 
Galvanometer, 
Galvanometer, Absolute 
Galvanometer, Aperiodic 
Galvanometer, Astatic 
Galvanometer, Ballistic 
Galvanometer Constant, 
Galvanometer, Differential 
Galvanometer, Direct Reading- 
Galvanometer, Marine 
Galvanometer, Mirror 
Galvanometer, Potential 
Galvanometer, Proportional 
Galvanometer, Quantity 
Galvanometer, Reflecting 
Galvanometer, Shunt . 
Galvanometer, Sine . 
Galvanometer, Tangent 
Galvanometer, Torsion 
Galvanometer, Upright 
Galvanometer, Vertical 
Galvanometer, Volt and 

Meter . 
Galvano-plastics, . 
Galvano-puncture, 
Galvanoscope, 
Galvano-thermal Cautery 
Gap, Spark 
Gas Battery, 
Gas Battery, Grove's 
Gas Burner, Electric 
Gas, Carbonic Acid 
Gas, Electrolytic 
Gases, Magnetism of 
Gases, Mixed 
Gas Jet, Carcel 
Gas, Olefiant 
Gassing, 

Gassiot's Cascade, 
Gastroscope, . 
Gas Voltameter, 
Gauge, Battery 
Gauge, Electrometer 
Gauss, 

Gauss' Principle, 
Gauss, Tangent Positions of 
Gauze Brush, Wire . 
Gear, Magnetic 
Gear, Magnetic Friction 
Geissler Pump, 
Geissler Tubes, 



Ampe 



271 



273-i 



232-! 



119 
, 156 
265 
262 
265 
265 
265 
265 
109 
265 
109 
265 
265 
266 
266 
266 
267 
268 
268 
, 269 
269 
271 
269 
269 
269 
270 
483 
271 
270 
544 
27- 
274 

274 
275 
275 
W~5 
109 
4'JO 

63 
281 

93 
108 
275 
357 
275 
108 
397 
275 
275 
275 
564 

64 
226 
275 
276 
276 

92 
346 
276 
437 
276 



Page. 
Generating Plate, . . .277 

Generator, Current . . . 277 

Generator Inductor, . . .199 
Generator, Magneto-electric . . 362 
Generator, Magneto-electric, Flash- 
ing in a Dynamo or . . 257 
Generator, Motor .... 384 
Generator, Pyromagnetic 442 

Generators and Motors, Commuta- 
tor of Current .... 140 
Generator, Secondary . . 277-477 
Geographic Meridian. . . . 372 
German Mile Unit of Resistance, / 466 
German Silver, .... 277 
German Standard Candle, . . 99 
Gilding, Electro- .... 277 

Gilding Metal, 277 

Gimbals 278 

Girder Armature, . . . .49 

Glass, 278 

Globe or Globular Lightning, . 330 

Glow Discharge, .... 187 

Gold, 278 

Gold Bath, 279 

Gold Leaf Electroscope, . . .233 
Gold Stripping Bath, . . . 279 
Governor, Centrifugal . . .113 
Governor, Rate .... 449 

Graduator, 279 

Gram, 280 

Gram-atom, 280 

Gram-molecule, .... 280 

Graphite 280 

Gravitation, 280 

Gravity, Acceleration of . . 280 

Gravity Ammeter, ... 27 

Gravity Battery, . . . .64 
Gravity, Centre of . . .112 

Gravity Control, . . . .281 
Gravity D p Annunciator, . 35 

Grease Spot, 92 

Green Vitriol, .... 562 

Grenet Battery, . . . .65 

Grid, 281 

Grid Plug, . . . ! .420 

Grip, Cable 96 

Gross Efficiency, .... 205 

Ground, 281 

Grounded Circuit, .... 123 
Ground Plate, .... 417 
Ground Wire, . . . . .281 
Grove's Battery, .... 65 
Grove's Gas Battery, . . .281 

Guard Ring, 282 

Guard Tube 282 

Gun, Electro-magnetic . . 282 

Gutta Percna 282 

Gyration, Centre of . . .112 
Gyrostatic Action of Armatures, . 283 

H, 283 

H Armature, 49 



INDEX. 



653 



Page. 

Haarlem Magnet, . . . .337 
Hair, Removal of, by Electrolysis 283 
Haldat's Figures, . . . .284 

Hall Effect, 284 

Hall Effect, Real . . . .284 
Hall Effect, Spurious . . .284 
Halleyan Lines, 
Hall's Experiment, . . .284 
Halske's and Siemens' Battery, , 72 

Hand Hole, 190 

Hanger Board, 284 

Hanger, Cable 
Hanger, Cable, Tongs 
Harcourt's Pentane Standard, 
Hare's Deflagrator, . 
Harmonic, .... 
Harmonic Curve, 
Harmonic Motion, Simple . 
Harmonic Receiver, 
Head Bath, Electric 
Head-light, Electric . 
Head, Torsion 

Heat 

Heat and Fire Alarm, . 

Heat, Atomic 

Heat, Electric 

Heat, Electric, Convection of 

Heat, Irreversible . 

Heat, Mechanical Equivalent of 

Heat, Molecular . 

Heat, Specific . 

Heat, Specific, of Electricity 

Heat Units, 

Heater, Electric 

Heating, Admiralty Rules of 

Heating Error, 

Heating, Frictional 

Heating Magnet, 

Heavy Carburetted Hydrogen 

Hecto, 

Hedgehog Transformer, 
Heliograph, . 
Helix, . ■ . . . . .288 

Henley's Universal Discharger, . 189 

Henry .288 

Henry's Coils, .... 138 

Hermetically Sealed . . .289 

Hertz's Experiments, . . . 470 

Heterostatic Method, 

Hexode Working, . . .581 

High Bars of Commutator, . . 289 

High Frequency, 

High Vacuum, .... 537 

Hinged Armature, ... 45 

Hinged Electro-magnet, . .217 

Hissing, 289 

Hittorf's Resistance, . . .466 
Hittorf's Solution, . . .289 

Hoffer's Method of Magnetization, 360 
Hole Armature, .... 45 

Hole, Hand 190 

Holders, .... 



. 97 

406 

. 73 

23 

4-485 

486 

284-451 

284 

. 285 

544 

. 285 

17 

52-285 

285 

149-286 

286 



286 
. 286 

288 
. 288 

286 
. 12 

286 
. 262 

286 
. 397 

288 
. 548 



Holder, Brush . 

Holder, Candle 

Holders, Carbon 

Holophote Lamp. 

Holtz's Influence Machine, 

Home Station, 

Hood, 

Horizontal Induction, . 

Horns, 

Horns, Driving 

Horns, Following 

Horns, Leading 

Horns, Trailing 

Horse Power, 

Horse Power, Actual 

Horse Power Curve, 

Horse Power, Electric 

Horse Power Hour, 

Horse Power, Indicated 

Horseshoe Magnet, 

Hour, Ampere- . 

Hour, Horse Power 

H. P. 



Heavy 



Hughes' Electro-magnet, 

Hughes' Induction Balance, 

Hughes' Sonometer, 

Hughes' Telegraph 

Hughes' Theory of Magnetism 

Hughes' Type Printer, 

Human Body, Resistance of 

Hydrochloric Acid Battery, 

Hydro-electric, 

Hydro-electric Machine 

Hydrogen, 

Hydrogen, Carburetted 

Hydrometer, Beaume 

H v grometer, 

Hyperbolic Logarithms 

Hysteresis, 

Hysteresis, Magnetic 

Hysteresis, Static 

Hysteresis, Viscous 

Idioelectrics, 

Idiostatic Method, . 

Idle Coils, 

Idle Poles, 

Idle Wire, 

Igniter, 

I. HP., . 

Illuminating Power, 

Illuminating Power, Spherical 

Illuminating Power, Standard 

Viole's 
Illumination, Unit of 
Image, Electric 
Imbricated Conductor, 
Immersion, Simple . 
Impedance, 
Impedance, Impulsive 
Impedance, Oscillatory 



Page. 
. 91 



. 107 

321 
. 334 

493 
. 290 

302 
. 290 

1^2 
. 259 

324 
. 259 

290 
. 290 

171 
. 290 

290 
. 290 

337 
. 30 

290 
. 290 

291 
. 291 

488 
. 511 

357 
. 511 

467 



293 
. 293 

294 

. 397 

78 

. 294 

389 
. 295 

294 

. 295 

295-3o6 



of, 



295 
, 295 
295 
296 
291 
296 
296 
296 
296 



561 



296 
146 

. 185 
297-462 

. 297 
297 



Impressed Electro-motive Force, . 297 



654 



INDEX. 



Page. 

Impulse 297 

Impulsive Discharge, . . . 188 
Impulsive Impedance, . . 297 
In-and-out, Soaking .... 486 
Incandescence, Electric . . 297 
Incandescent Lamp, . . . 321 
Incandescent Lamp Carbons, Flash- 
ing of 257 

Incandescent Lamp, Chamber of 113 
Incandescent Lamp, Life of . . 327 
Incandescent Lamp, Three Fila- 
ment 322 

Inclination Compass, . . . 142 
Inclination, Magnetic . . . 346 

Inclination Map 297 

Inclination or Dip, Angle of . .33 
Incomplete Circuit, . . . 125 
Increment Key, .... 314 
Independence of Currents in Paral- 
lel Circuits, 297 

India Rubber, .... 102 
Indicated Horse Power, . . . 290 
Indicating Bell, . . . 80-297 

Indicator, 298 

Indicator, Circuit .... 298 
Indicator, Throw-back . . . 540 
Indicator, Volt . . . .568 
Indifferent Electrode, . . .210 
Indifferent Point, .... 421 
Induced Current, .... 163 
Induced Magnetization, Coefficient 
of . . . . . . 354-359 

Inductance, 298 

Inductance Balance, . . . 293 

Inductance Bridge, . . . 29$ 
Induction, Anti-, Conductor . . 36 
Induction, Back .... 55 
Induction Balance, Hughes' . . 291 
Induction, Coefficient of Magnetic 349 
Induction, Coefficient of Mutual . 301 
Induction, Coefficient of Self- . 298 

Induction Coil, 133 

Induction Coil, Inverted . . 136 
Induction Coil, Telephone . 137-526 
Induction, Cross .... 298 
Induction Current, .... 163 
Induction, Electro-magnetic 218-299 
Induction, Electrostatic . . . 302 
Induction, Electrostatic, Coefficient 

of 234 

Induction, Horizontal . . . 302 
Induction, Lateral .... 302 
Induction, Lines of 330 
Induction, Magnetic . . 302-346 
Induction, Magnetic, Apparent Co- 
efficient of 346 

Induction, Magnetic, Coefficient of 346 
Induction, Magnetic, Dynamic . 347 
Induction, Magnetic, Self- . . 352 
Induction, Magnetic Static . . 347 
Induction, Magnetic, Tube of . 347 



Mutual, 



Page. 
Electro-mag- 



of 



. 305 

. 305 

. 347 

305-420 

. 305 

. 334 

46 

. 334 

. 346 



Induction 
netic 

Induction, Mutual, Electrostatic . 303 
Induction, Open Circuit . . 303 
Induction, Oscillatory . . . 398 
Induction Protector, Mutual . 481 
Induction, Self- .... 303 

Induction Sheath, .... 303 
Induction, Unipolar . . . 304 

Induction, Unit of Self- . . 304 
Induction, Vertical .... 304 
Inductive Capacity, Magnetic 346-349 
Inductive Effect, Counter- . . 204 
Inductive Resistance, . . . 466 

Inductophone, 304 

Inductor, 305 

Inductor Dynamo, . . . .199 
Inductor Generator, . . . 199 
Inductor, Magneto- . . . .363 
Inductor, Pacinotti's . . . 400 
Inductorium, 

Inertia, 

Inertia, Electro-magnetic 

Inertia, Magnetic . 

Infinity Plug, . 

Influence, V lectric 

Influence Machine, . 

Influence Machine, Armature 

Influence Machine, Holtz 

Influence, Magnetic 

Installation, 

Instantaneous Capacity, 

Insulating Stool, 

Insulating Tape, 

Insulating Varnish, . 

Insulation, Electric 

Insulation, Magnetic 

Insulation, Oil 

Insulation Resistance, 

Insulator, .... 

Insulator Caps, . 

Insulator, Fluid 

Insulator, Line or Telegraph 

Intensity, .... 

Intensity Armature, . 

Intensity Current, 

Intensity, Electro-motive 

Intensity, Magnetic 

Intensity of a Magnetic Field 

Intensity of Magnetization, 

Intensity, Poles of 

Inter-air Space, .... 489 

Intercrossing, 307 

Interference, Armature . . 45 
Interfecric Space, .... 489 
Interior Pole Dynamo, . .191 

Interlocking Electro-magnets . . 229 
Intermediate Metals, Law of . 323 

Intermittent, 307 

Internal Characteristic, . .114 
Internal Resistance, . . . 466 

Interpolar Conductor, . . 307 



102 
. 305 

305 
. 306 

305 
. 347 

396 
. 466 



306 



45 
163 



348 



360 
. 426 



INDEX. 



655 



Interpolar Region, . 

Interpolation, 

Interrupter, Electro-magnetic 

Tuning Fork 
Intrinsic Efficiency, 
Invariable Calibration 
Inverse Induced Current, 
Inverse Squares, Law of 
Inversion, Thermo-electric 
Ions, .... 

Iron, 

Ironclad Dynamo, 

Ironclad Electro-magnet, 

Ironclad Magnet, 

Iron Disc Ammeter, Eccentric 

Iron, Electrolytic 

Iron, Galvanized 

Ironwork Fault of a Dynamo, 

Irreversible Heat, 

Isochasmen Curve, 

Isochronism, 

Isoclinic Lines, 

Isoclinic Map, . 

Isodynamic Lines, 

Isodynamic Map, 

Isoelectric Points, , 

Isogonal Lines, 

Isogonic Map, 

Isolated Distribution, 

Isolated Plant, 

Isolated Supply, 

Isotropic, .... 

Isthmus Method of Magnetizat 

I. W. G., .... 



Jablochkoff Candle, . 

Jack, Spring- .... 

Jacketed Magnet, 

Jacobi's Law, 

Jacobi's Method of Magnetization 

Jacobi's Unit of Current, 

Jacobi's Unit of Resistance, 

Jamin Candle, 

Jar, Leyden 

Jar, Lightning 

Jar, Luminous .... 

Jars, Leyden, Charging and D 

charging .... 
Jar, Unit .... 

Jewelry, .... 

Joulad, 

Joule, 

Joule Effect, .... 

Joule's Electro-magnet, . 

Joule's Equivalent, 

Joint, American Twist, 

Joint, Britannia 

Joint, Butt 

Joint Current, 

Joint, Lap .... 

Joint, Marriage 



Page. 
. 307 

307 
for 

307 

. 205 

97 

. 163 

323 
. 533 

307 
. 308 

200 
. 219 

356 
. 27 

308 
. 265 

308 
. 286 

171 



. 308 



422 

308 
309 
309 
309 
309 



309 

309 
160 
492 
356 
309 
360 
163 
466 
100 
325 



332 

, 108 
554 

, 309 
311 
311 
311 
337 
311 
309 
309 
310 
160 
310 
310 



Joint, Resistance 
Joints in Belts, 
Joint, Sleeve 
Joint, Splayed 
Junction Box, . 
Junction, Thermo-electric 



K, .... 

Kaolin, 

Kapp, Line of Force 

Kathelectrotonus, 

Kathode, 

Kathodic Closure Contraction, 

Kathodic Duration Contraction, 

K. C. C. 

K. D. C 

Kempe's Discharge Key, 
Keeper, 
Kerr Effect, 
Kerr's Experiment, 

Key, 

Key Board, 

Key, Bridge 

Key, Double Contact . 

Key, Double Tapper 

Key, Charge and Discharge 

Key, Increment 

Key, Kempe's Discharge 

Key, Magneto-electric 

Key, Make and Break 

Key, Plug 

Key, Reversing 

Key, Sliding-contact 

Key, Telegraph 

Kicking Coil, 

Kilo, .... 

Kilodyne, 

Kilogram, 

Kilojoule, .... 

Kilometer, 

Kilowatt, .... 

Kine 

Kinnersley's Thermometer, 
Kinetics, Electro- . 
Kinetic Energy, 
Kirchoff's Laws, . 
Knife Break Switch, 
Knife Edge Suspension, 
Knife Edge Switch, 
Knife Switch, 
Knot, .... 

Kohlrausch's Law, 
Kookogey's Solution, 
Krizik's Cores, 



I*, . . . . 

Lag, Angle of 

Lag, Electric 

Lag, Magnetic 

Lalande & Chaperon Battery 

Lalande-Edison Battery, 



6 5 6 



INDEX, 



Page. 
Lamellar Distribution of Magnet- 
ism, 357 

Laminated, . . . . 318 
Laminated Core, .... 154 
Laminated Core, Tangentially . 155 
Lamination, . . . . . 318 
Lamination of Armature Conduc- 
tors, 319 

Lamination of Magnet, . . .361 

Lamp, Arc 319 

Lamp, Arc, Double Carbon . . 191 
Lamp Carbons, Flashing of Incan- 
descent 257 

Lamp, Carcel .... 108 

Lamp, Contact 320 

Lamp, Differential Arc . 320 

Lamp Globe, Waterproof . 572 

Lamp, Holophote . . . .321 

Lamp-hour, 321 

Lamp, Incandescent . . . 321 
Lamp, Incandescent, Chamber of . 113 
Lamp, Incandescent, Three Fila- 
ment 322 

Lamp, Life of Incandescent . 327 
Lamp, Lighthouse .... 322 
Lamp, Monophote . . . 321 

Lamp, Pilot 323 

Lamp, Polyphote .... 323 
Lamp, Semi-Incandescent . . 323 

Lamp-socket, 323 

Lamps, Bank of .... 323 

Lane's Electrometer, . . . 226 
Langdon Davies 1 Rate Governor or 

Phonophone, .... 450 
Lenz's Law, .... 325 

Lap Joint, . . .310 

Lap Winding, 579 

Latent Electricity, . . . 323 
Lateral Discharge, .... 188 
Lateral Induction, . . . 302 

Latitude, Magnetic . . . .348 
Law, Jacobi's . . . 309 

Law, Kohlrausch's .... 317 

Law, Lenz's 325 

Law of Angular Currents, . . 165 
Law of Electrolysis, . . .213 
Law of Intermediate Metals, . . 323 
Law of Inverse Squares, . . 323 
Law of Magnetic Attraction and 

Repulsion, Coulomb's . . 338 
Law of Successive Temperatures, 324 

Law, Magnus' 367 

Law, Ohm's 396 

Law, Pfluger's 409 

Law, Right Handed Screw . . 324 

Law, Sine 486 

Laws, Kirchoff's .... 317 
Laws of Thermo-electricity, Bec- 

querel's 78 

Law, Tangent .... 502 
Law, Voltametric . . . .567 
Lead 324 



Page. 

Lead, Angle of 33 

Lead Chloride Battery, . . 66 
Lead of Brushes, . . .90 

Lead of Brushes, Negative . . 324 
Lead, Peroxide of, Battery . 69 

Lead Sulphate Battery, . . 66 
Lead Tee, . . . . ' .504 

Leading Horns, .... 324 
Leading-in Wires, .... 324 

Leak, 324 

Leakage, 324 

Leakage Conductor, ... 325 
Leakage, Electro-magnetic . . 219 
Leakage, Magnetic . . . 348 
Leakage, Surface .... 498 
Leclanche Agglomerate Battery, 66 
Leclanche Battery, . . . .66 
Leg of Circuit, .... 325 

Legal Ohm, 395 

Legal Quadrant, .... 444 

Legal Volt, 568 

Length of Spark, . . . .490 
Letter Boxes, Electric . . .325 

Leyden Jar, 325 

Leyden Jar, Armature of . 46 
Leyden Jars, Battery of . . 68 
Leyden Jars, Charging and Dis- 
charging 108 

Leyden Jars, Sir William Thomson's 326 
Lichtenberg's Figures, . . 327 

Life Curve, 171 

Life of Incandescent Lamp, . 327 

Light, Electro-magnetic, Theory of 219 
Light, Maxwell's Theory of . . 369 
Lighthouse Lamp, ... 322 

Lightning, .... 327 

Lightning Arrester, . . . 328 
Lightning Arrester, Counter-elec- 
tro-motive Force . . . 329 
Lightning Arrester Plates, . . 329 
Lightning Arrester, Vacuum . 329 
Lightning, Ascending . . . 330 
Lightning, Globe or Globular . 330 

Lightning Jar, 330 

Lightning, Back Stroke or Shock 

of 55 

Lime, Chloride of, Battery . . 61 
Limit, Magnetic . . . .348 
Limit of Magnetization, . . 361 
Linear Current, .... 164 

Lineman's Detector, . . .180 
Line of Commutator, Neutral . 390 

Line of Contact, .... 330 
Line of Force, Kapp . . .312 
Line of Magnet, Neutral . . 361 
Line or Telegraph Insulator, . . 306 
Lines, Halleyan .... 308 

Lines, Isoclinic 308 

Lines, Isodynamic .... 308 
Lines, Isogonal .... 308 

Lines, Isogonic .... 308 
Lines of Force, . . . .330 



INDEX. 



657 



Page. 
Lines of Force, Cutting of . . 175 
Lines of Force, Electro-magnetic . 219 
Lines of Force, Electrostatic . 234 
Lines of Force, Magnetic . . 348 
Lines of Induction, . . . 330 

Lines of Slope, 330 

Lines or Points of Least Sparking, 490 

Lines, Trunk 550 

Links, Fuse 330 

Liquids, Electro-dynamic Rotation 

of 474 

Liquids, Electro-magnetic Rotation 

of 475 

Liquor, Spent 491 

Listening Cam, .... 330 

Lithanode, 331 

. 331 

. 172 

46 

. 331 

. 331 

. 331 

163-331 

. 331 

. 331 

. 332 

. 332 

. 389 

. 389 

. 66 

. 361 

220 



Load, 

Load Curve, 

Load of Armature 

Local Action, 

Local Battery, 

Local Circuit, . 

Local Currents, 

Localization, .... 

Locus, 

Lodestone, .... 

Logarithm, 

Logarithms, Hyperbolic . 

Logarithms, Napierian . 

Local Battery, .... 

Long Coil Magnet . . . 

Long Range Electro-magnet, 

Long Shunt and Series Winding, 

Long Shunt Winding, 

Loop, 

Loop Break, 

Loop, Circuit 

Loop, Drip 

Lost Amperes, 

Lost Volts, 

Low Vacuum, 

Luces, 

Luminous Jar, 

Luminous Pane, 

Luminous Tube, 

Lux, 



. 579 

332 
. 332 

125 

. 192 

30 

. 571 

557 
. 332 

332 
. 401 

550 
. 332 



M f 332 

Machine, Cv Under Electric . . 333 
Machine, Electric, W T imshurst . 577 

Machine, Frictional Electric . 333 
Machine, Holtz Influence . . 334 

Machine, Hydro-electric . . 293 
Machine, Influence .... 334 
Machine, Nairne's Electrical . 389 
Machine, Plate Electrical . . 417 
Machine, Rheostatic . . . 472 
Machine, Toeppler-Holtz . . 334 

Machine, Wimshurst . . . 335 
Mack, . . .... 335 

Magic Circle, 119 

Magne-crystallic Action, . . .335 



Page. 
Magnet, . . . . .335 

Magnet, Anomalous . . . 335 

Magnet, Artificial . . . .335 

Magnet, Axial 336 

Magnet, Bar 336 

Magnet, Bell Shaped . . .336 
Magnet Coils, Sheath for . . 481 
Magnet, Compensating . . . 336 
Magnet, Compound . . .336 
Magnet, Controlling . . 185-336 

Magnet, Damping . . .336 

Magnet, Deflection of 337 

Magnet, Directing . . .185 

Magnet, Electro- . . . 215-337 
Magnet, Equator of 337 

Magnet, Field 337 

Magnet, Haarlem . . .337 

Magnet, Heating . . . .286 
Magnet, Horseshoe . . . 337 
Magnet, Ironclad .... 356 
Magnet, Joule's Electro- . . 337 
Magnet-keeper, .... 361 

Magnet, Lamination of . . 361 

Magnet, Long Coil . . . .361 
Magnet, Natural . . . .361 
Magnet, Neutral Line of . . 361 

Magnet, Normal .... 361 
Magnet Operation, .... 365 
Magnet, Permanent . . . 365 

Magnet Pole, 365 

Magnet, Portative Power of . 366 
Magnet, Projecting Power of a . 435 
Magnet, Relay .... 457 
Magnet, Simple . . . .366 

Magnet, Solenoidal . . . 366 
Magnet, Sucking . . . 366 

Magnet, Unipolar . . . 366 

Magnet Coil, . ... 336 

Magnet Core, . . . 336 

Magnet Poles, Secondary . . 366 
Magnet Pole, Unit . . .366 

Magnetic Adherence, . . . 338 
Magnetic and Electro-magnetic 

Equipotential Surface, . . 244 
Magnetic Attraction, . . . 338 

Magnetic Attraction and Repulsion, 

Coulomb's Law of 338 
Magnetic Axis, .... 338 
Magnetic Azimuth, .... 338 
Magnetic Battery, . . . 338 
Magnetic Bridge, .... 338 
Magnetic Circuit, .... 340 
Magnetic Circuit, Curve of Satura- 
tion of 174 

Magnetic Concentration of Ores, . 340 
Magnetic Concentrator, . . 340 
Magnetic Continuity, . . . 340 
Magnetic Conductance and Con- 
ductivity, .... 340 
Magnetic Control, .... 341 
Magnetic Couple, .... 341 
Magnetic Creeping, .... 341 



6sS 



INDEX. 



Page. 
Magnetic Curves, .... 341 
Magnetic Cut Out, . . . . 175 
Magnetic Declination, . . . 342 
Magnetic Density, .... 342 
Magnetic Dip, . . . 342-346 
Magnetic Discontinuity, . . 342 

Magnetic Double Circuit, . . 340 
Magnetic Eye, Electro- . . .248 
Magnetic Elements, . . . 342 
Magnetic Elongation, . . . 344 
Magnetic Equator, . . . 344 
Magnetic False Poles, . . . 350 
Magnetic, Ferro- .... 252 
Magnetic Field, Intensity of a . 306 
Magnetic Field of Force, . . 344 
Magnetic Field, Uniform . . 345 
Magnetic Figures, . . . 345 

Magnetic Filament, . . . 345 

Magnetic Fluid, North . . 357 

Magnetic Fluids, .... 345 
Magnetic Flux, .... 345 
Magnetic Force, .... 346 
Magnetic Friction, . . 295-346 
Magnetic Friction Gear, . . . 276 
Magnetic Fluid, South . . 356 

Magnetic Foci, 259 

Magnetic Gear, .... 346 
Magnetic Hysteresis, . . . 294 
Magnetic Inclination, . . . 346 
Magnetic Induction, . . . 302 
Magnetic Induction, Apparent Co- 
efficient of 346 

Magnetic Induction, Coefficient 

of 346-349 

Magnetic Induction, Dynamic . 347 
Magnetic Induction, Static . . 347 
Magnetic Induction, Tube of . 347 
Magnetic Inductive Capacity, . 349 

Magnetic Inertia, .... 347 
Magnetic Influence, .... 346 
Magnetic Insulation, . . . 347 
Magnetic Intensity, .... 348 
Magnetic Lag, . . . .348 

Magnetic Latitude 348 

Magnetic Leakage, . . . 348 
Magnetic Limit, .... 348 

Magnetic Lines of Force, . . 348 
Magnetic Mass, .* 349 

Magnetic Matter, .... 349 
Magnetic Memory, . . . . . 349 
Magnetic Meridian, . . . 349 
Magnetic Moment, .... 349 
Magnetic Needle, . . . .349 
Magnetic Needle, Declination of 

the 178 

Magnetic Needle, Dip of . .185 

Magnetic Needle, Oscillation of a 397 
Magnetic Output, . . . .399 
Magnetic Parallels, . . .849 
Magnetic Permeability, . . . 349 
Magnetic Perturbations, . . 350 
Magnetic Poles, .... 350 



Page. 
Magnetic Potential, . . 350-431 
Magnetic Proof Piece, . . . 350 
Magnetic Proof Plane, . . 350 

Magnetic Quantity, . . . . 350 
Magnetic Reluctance, . . 351-458 
Magnetic Reluctivity, . . . 351 
Magnetic Remanence, . . . 358 
Magnetic Repulsion, . . . 338 
Magnetic Resistance, . . . 458 
Magnetic Retentivity, . . .351 
Magnetic Rotatory Polarization, 351 
Magnetic Saturation, . . .251 
Magnetic Screen, .... 351 
Magnetic Self-induction, . . 352 

Magnetic Separator, . . . 352 
Magnetic Shell, . . . .352 

Magnetic Shell, Strength of . 352 

Magnetic Shield, .... 353 
Magnetic Shunt, .... 353 
Magnetic Storms, .... 353 
Magnetic Strain, .... 354 
Magnetic Stress, .... 354 
Magnetic Susceptibility, . 254-359 

Magnetic Tick, 354 

Magnetic Top, .... 542 
Magnetic Twist, .... 354 
Magnetic Vane Ammeter, . . 27 
Magnetic Variations, . . . 354 
Magnetism, Ampere's Theory of 354 
Magnetism, Blue ..... 355 
Magnetism, Components of Earth's 356 
Magnetism, Creeping of . . 356 

Magnetism, Decay of . . . 356 
Magnetism, Discharge of . . 356 

Magnetism, Electro- . . . 220 
Magnetism, Ewing's Theory of . 356 
Magnetism, Free .... 356 
Magnetism, Hughes' Theory of . 357 
Magnetism, Lamellar Distribution 

of 357 

Magnetism of Gases, . . . 357 
Magnetism, Red .... 357 

Magnetism, Residual . . 358 

Magnetism, Solenoidal Distribution 
of ....... 3"8 

Magnetism, Sub-permanent . . 358 
Magnetism, Terrestrial . . 358 
Magnetism, Weber's Theory of . 358 
Magnetization by the Earth, . 359 
Magnetization by Double Touch, . 358 
Magnetization by Separate Touch, 359 
Magnetization by Single Touch, . 359 
Magnetization, Coefficient of In- 
duced 359 

Magnetization Curve, . . . 172 
Magnetization, Cycle of . . . 360 
Magnetization, Elias' Method of 360 
Magnetization, Hoffer's Method of 360 
Magnetization, Intensity of . 360 

Magnetization, Isthmus Method of 360 
Magnetization, Jacobi's Method . 360 
Magnetization, Limit of . . . 361 



INDEX. 



659 



r, 



Page. 
. 361 

361 
. 356 

127 

. 361 

80 

. 361 

361 
. 362 

362 



257 
315 
512 
363 
363 
363 
365 
364 
365 
367 
365 
28 
367 



Magnetization, Maximum 
Magnetization, Specific 
Magnetization, Surface . 
Magnetizing Coil, 
Magneto, .... 
Magneto Bell, 
Magneto Call Bell, . 
Magneto-electric, . 
Magneto-electric Brake, . 
Magneto-electric Generator, 
Magneto-electric Generator, 

Dynamo, Flashing in a 
Magneto-electric Key, . 
Magneto-electric Telegraph 
Magnetograph, 
Magneto-inductor, 
Magnetometer, 
Magnetometer, Differential 
Magnetometry, 
Magneto-motive Force, . 
Magnetophone, 
Magnetoscope, . 
Magnifying Spring Ammete 
Magnus' Law, . 
Main Battery, 
Main Battery Circuit, 
Main Circuit, . 
Main or Standard Feeder, 
Mains, Electric 

Make, 

Make and Break Current, 

Make and Break Key, 

Make-induced Current, 

Malapterurus, . 

Map, Declination . 

Map, Inclination 

Map, Isoclinic 

Map, Isodynamic 

Map, Isogonic 

Marie Davy's Battery, 

Marine Galvanometer, 

Mariner's Compass, . 

Marked End or Pole, 

Marriage Joint, 

Mass, Electric 

Mass, Magnetic 

Master Clock, 

Mathematical Element, . 

Matteueci's Experiment, 

Matter, Electric 

Matter, Fourth State of 

Matter, Magnetic 

Matter, Radiant 

Matter, Ultra Gaseous 

Matthiessen's Meter-gram Standard 

Resistance, .... 
Matthiessen's Unit of Resistance 
Matting, Electric Floor . . . 369 
Maximum Magnetization, . . 361 
Maxwell's Theory of Light, . . 369 
Mayer's Floating Magnet, . . 370 
Maynooth's Battery, . . 67 



125 

125 
251 

36; 

367 

164-367 

. 316 

163 



297 



309 
67 
269 
142 
368 
310 
368 
349 
127 
237 
369 
368 
261 
349 
368 
551 

466 



Page. 

Measurement, Absolute . . 8 

Measurements, .... 370 

Mechanical Equivalent of Heat, 286 
Mechanical Energy, . . . 241 

Mechanical Equivalent, Electro- 244 
Medical Battery, . . . .67 
Medium, Polarization of the . 424 

Meg or Mega, 370 

Meidinger's Battery, ... 68 
Memoria Technica, Ampere's . 30 

Memory, Magnetic . . . 349 

Mercury, 371 

Mercury Bichromate, Battery, . 63 
Mercury Circuit Breaker, . .121 
Mercury Cups, . . . .371 
Mercury, Sulphate of, Battery . 67 
Mercurial Air Pump, ... 16 
Meridian, xlstronomical . . . 372 
Meridian, Geographic . . . 372 
Meridian, Magnetic .... 349 
Merit, Figure of . . . .256 
Merit, Formula of . . 256 

Metal, Gilding .... 277 

Metallic Arc 39 

Metallic Circuit, . . . .125 
Metallochromes, .... 392 
Metallurgy, Electro- . . 222 

Metals, Law of Intermediate . . 323 
Meter, Alternating Current . 373 

Meter, Ampere and Volt, Galvan- 
ometer . .... 274 
Meter, Balance Ampere . . 391 

Meter Bridge, 373 

Meter Bridge, Slide . . .486 

Meter Candle, 374 

Meter, Chemical Electric . . 375 

Meter, Current 375 

Meter, Electro-magnetic . . 375 

Meter, Energy 375 

Meter Gram Standard Resistance, 

Matthiesen's . . . .466 
Meter-millimeter, .... 375 
Meter-millimeter Unit of Resistance 466 
Meter, Neutral Wire Ampere . . 391 
Meter, Quantity .... 445 
Meters, Ampere . . . .30 

Meter, Thermal-Electric . . 375 
Meter, Time Electric . . . 375 

Meter, Watt 375 

Method, Broadside . . . .89 
Method, Deflection . . .178 
Method, End on .... 238 
Method, Idiostatic . . . 295 

Method, Multiple Wire . . .388 
Method, Null .... 393 

Method of Magnetization, Elias' . 360 
Method of Magnetization, Isthmus 360 
Method of Magnetization, Jacobi's 360 
Methven Standard or Screen, . . 376 

Mho .376 

Mica 376 

Mica, Moulded .... 376 



66o 



INDEX. 



Page. 

. 376 

376 

39-376 

470 

. 376 



Micro, .... 

Micrometer, . • 
Micrometer, Arc 
Micrometer, Spark 
Micron, .... 
Microphone, .... 376 

Microphone Relay, . . . 377-457 
Microscope, Photo-electric . . 410 
Microtasimeter, .... 377 

Mil, . 379 

Mil, Circular 379 

Mil-foot, 379 

Mil-foot Unit of Resistance, . . 467 

Milli, 379 

Milligram, 379 

Millimeter, 379 

Milli-oerstedt, 380 

Mil, Square 379 

Minute, Ampere- . . . .30 
Mirror Galvanometer, . . . 271 

Mixed Gases, 275 

mm., 380 

Molar, 380 

Molar Energy, . . . .241 
Molecular Affinity, .... 380 
Molecular Attraction, . . . 380 
Molecular Bombardment, . 380 

Molecular Chain, . . . .380 
Molecular Energy, .... 241 

Molecular Heat 286 

Molecular Rigidity, . . . 380-473 
Molecular Shadow, . . 480 

Molecule, 380 

Moment, 381 

Moment, Magnetic .... 349 
Moment of Couple, . . . 544 
Moment, Turning .... 544 
Monophote Lamp, . . . 321 

Mordey Effect, . . . .381 

Morse Receiver, .... 381 

Morse Recorder 451 

Morse Telegraph, . . . 512 

Mortar, Electric . . . .382 
Motion, Currents of 167 

Motograph, Electro- . . .229 

Motor, Compound or Compound 

Wound, 382 

Motor, Differential . . . .382 
Motor, Dynamo .... 200 
Motor, Electric .... 382 

Motor, Electro- .... 229 
Motor, Electro-motive Force . . 384 
Motor-generator, .... 384. 

Motor, Multiphase 384 

Motor, Overtype . . .399 

Motor, Prime 385 

Motor, Pulsating . . . .386 
Motor, Pyromagnetic . . . 442 
Motor, Reciprocating . . . 385 

Motor, Series 386 

Motor, Shunt . . . .386 
Moulded Mica, 376 



Moulding, .... 
Movable Secondary, 
Mud, Battery 
Multiphase Currents, 
Multiphase Motor, 

Multiple, 

Multiple Arc, 
Multiple Arc Box, 
Multiple Connected Battery, 
Multiple-series, 
Multiple Switch, . 
Multiple Switch Board, . 
Multiple Transformer, . 
Multiple Winding, 
Multiple Wire Method, 
Multiplex Harmonic Telegraph, 
Multiplex Telegraph, . 
Multiplex Telegraphy, 
Multiplier, Schweigger's 
Multiplying Power, . 
Multiplying Power of a Shunt, 
Multipolar Armature, 
Multipolar Dynamo, 
Multipolar Electric Bath, 
Multipolar Winding, 

Muscular Pile, 

Mutual Electro-magnetic Induction, 
Mutual Electrostatic Induction, 
Mutual Induction, Coefficient of 
Mutual Induction Protector, . 
Myria, .... 



34' 



^Jaime's Electrical Machine 
Napierian Logarithms, . 
Nascent State, . 
Natural Currents, . 
Natural Magnet, 

Needle, 

Needle Annunciator, 
Needle, Astatic 
Needle, Dipping 
Needle, Magnetic . 
Needle, Orientation of a Magnet 
Needle of Oscillation, . 
Needle Telegraph, Single 
Needle, Telegraphic 
Negative Charge, 
Negative Current, 
Negative Electricity, 
Negative, Electro- 
Negative Element, . 
Negative Feeder, 
Negative Lead of Brushes, 
Negative Plate, 
Negative Pole, 
Negative Potential, 
Negative Side of Circuit, 
Nerve and Muscle Current, 
Nerve Currents, 
Net Efficiency, 
Net, Faraday's 
Network, 



166-389 
. 361 



477 

68 
166 
384 
386 
387 
387 

68 
-480 
501 
387 
548 
579 
388 
510 
514 
388 
476 
-349 
388 

46 
200 

57 
579 
388 
302 
303 
301 
481 
388 



. 389 
389 



35 
50 

185 

349 

ic 397 

389 

. 519 
38U 

. 389 
164 

. 389 
229 

, 390 
251 
324 
417 
425 
432 
125 
164 
390 
205 
250 
390 



INDEX. 



661 



Neutral Armature, . 
Neutral Feeder, 
Neutral Line of Commutator, 
Neutral Line of Magnet, 
Neutral Point, .... 
Neutral Point of Commutator, 
Neutral Point, Thermo-electric 
Neutral Relay Armature, 
Neutral Temperature, 
Neutral Wire, 
Neutral Wire Ampere Meter, 
N. H. P., ... 

Niaudet's Battery, . 
Nickel, .... 
Nickel Bath, 
Night Bell, . 
Nitric Acid Battery, 
Nobili's Rings, 
Nodal Point, 
Nodular Deposit, . 
Nominal Candle Power, . 
Non-conductor, 
Non-essential Resistance, 
Non-inductive Resistance, 
Non-polar Dynamo, . 
Non-polarizable Electrodes, 
Non-Polarized Armature, 
Normal Magnet, . 
North Magnetic Fluid, 
North Pole, . 
North Seeking Pole, 
Null Method, 
Null Point, 



Occlusion, 

Oerstedt 

Oerstedt's Discovery, . 
Oerstedt, Milli- 

Ohm 

ohmage, . 

Ohm, B. A. . 

Ohm, Board of Trade 

Ohm, Congress 

Ohmic Resistance, . 

Ohm, Legal . 

Ohmmeter, 

Ohm, Rayleigh 

Ohm's Law, 

Ohm, True . 

Oil Insulation, . 

Oil Transformer, . 

Old Armature, Siemens' . 

Olefiant Gas, . 

Omnibus Bar, 

Omnibus Rod, 

Omnibus Wire, . 

One Coil Electro-magnet, 

Open, 

Open Circuit, 
Open Circuit Battery, 
Open Circuit Induction, 
Open Circuit Oscillation. 



Page. 



251 
. 390 

361 
. 421 

390 

. 390 

46-390 

. 390 

390 
. 391 

391 
. 61 

391 
. 391 

392 



39<3 
. 422 

392 
. 101 

392 
465-467 

467 
. 200 

210 
. 46 

*36l 
. 357 

392 
. 393 

393 
. 422 



393 
394 
394 



394 

. 394 

394 

. 394 

395 

394-467 

395 

395 

390 

390 



396 

548 

49 

397 

94 

94 

94 

219 

397 

125 

68 

303 

, 397 



54- 



Open Coil Armature, . 
Open Coil Dynamo, 
Opening Shock, 
Operation, Magnet . 
Opposed Current, 
Optics, Electro- 
Orders of Currents, 
Ordinate, .... 
Ordinates, Axis of 
Ores, Electric Reduction of 
Ores, Magnetic Concentration of 
Organ, Electric 

Orientation of a Magnetic Needle, 
Origin of Co-ordinates, . 
Oscillation, Centre of . 
Oscillation, Electric . 
Oscillation, Needle of . 
Oscillation, Open Circuit 
Oscillatory, 
Oscillatory Discharge, 
Oscillatory Displacement 
Oscillatory Electro-motive Force 
Oscillatory Impedance, 
Oscillatory Induction, 
Osmose, Electric . 
Outlet, 

Output, .... 
Output, Magnetic 
Output, Unit of . 
Over-compounding, . 
Over, Flashing 
Overflow Alarm, 
Over-house Telegraph, 
Overload, .... 
Overtype Dynamo or Motor 
Oxide of Copper Battery, 
Ozone, .... 



I»acinotti's Inductor, 

Pacinotti's Ring, . 

Pacinotti Teetrj, 

Page Effect, . 

Page's Revolving Armature, 

Paillard Alloys, 

Palladium, . 

Pane, Fulminating 

Pane, Luminous 

Pantelegraphy, 

Paper Filaments, 

Parabola, 

Parabolic Reflector, . 

Paraffine, 

Paraffine Wax, . 

Paragreles, 

Parallax, 

Parallel 

Parallel Circuits, 
Parallelogram of Forces, 
Parallels, Magnetic . 
Paramagnetic, 
Paramagnetism, 
Parasitical Currents, 



46 
200 
482 
365 
164 
229 
167 
397 
397 
453 
340 
397 
397 
397 
112 
398 
389 
397 

23 
188 
398 
398 
297 



399 



258 
18 
515 
399 
399 
68 



400 
400 
400 
401 
47 
400 
401 
262 

. 401 
402-510 
402 
402 
402 
402 
402 
403 
403 
403 
123-126 
260 

. 349 
403 

. 404 
163 



662 



INDEX. 



Page. 

. 404 

. 164 

203-404 

. 557 



Parchmentizing, 
Partial Current, 
Partial Earth, . 
Partial Vacuum, 

Passive State, 404 

Path, Alternative .... 24 

P. D 404 

Peltier's Cross, .... 405 

Peltier Effect, 404 

Pen, Electric . . . .405 

Pendant Cord, 405 

Pendulum Circuit Breaker, . . 121 
Pendulum, Electric .... 405 
Pendulum or Swinging Annuncia- 
tor 35 

Pentane Standard, Harcourt's . 406 
Pentode Working, . . .581 

Percussion, Centre of . .112 

Perforated Armature, ... 45 
Perforated Core Discs, . . . 154 

Perforator, 407 

Period, 407 

Period, Vibration .... 560 

Periodic, 23 

Periodic Current, Power of . 433 

Periodicity, .... 262-408 

Peripolar Zone, .... 582 

Permanency, 408 

Permanent Magnet, . . . 365 
Permanent Magnet Ammeter, . 28 

Permanent State, .... 408 

Permeability 346-349 

Permeability-temperature Curve, 174 

Permeameter, 408 

Permeance, 408 

Peroxide of Lead Battery, . . 69 
Perturbations, Magnetic . . 350 

Pfluger's Law, 409 

Phantom Wires, .... 409 

Phase, 409 

Phase, Retardation of . . . 471 
Phenomenon, Porret's . . . 427 
Pherope, . . . 409-527 

Philosopher's Egg, .... 409 
Phonautograph, .... 409 

Phone, 409 

Phonic Wheel, .... 409 

Phonograph, 410 

Phonophone or Rate Governor, 

Langdon Davies' . . . 450 
Phonozenograph, .... 410 
Phosphorescence, .... 410 
Phosphorous, Electrical Reduction 

of 410 

Photo-electric Microscope, . . 410 
Photo-electricity, .... 410 
Photo-electro-motive Force, . . 410 

Photometer, 411 

Photometer, Actinic . . . 411 

Photometer, Bar . . . .411 
Photometer, Bunsen's . . . 412 
Photometer, Calonmetric . . 412 



Photometer, Dispersion . 


. 412 


Photometer, Shadow 


. 414 


Photometer, Translucent Disc . 412 


Photophore, . 


. 415 


Photo-voltaic Effect, 


. 415 


Physical Energy, . 


. 241 


Physiology, Electro- 


. 231 


Piano, Electric 


. 415 


Pickle, .... 


. 415 


Picture, Electric . 


. 415 


Piece, Bed .... 


. 78 


Piece, Magnetic Proof . 


. 350 


Piece, Pole 


. 423 


Pierced Core-discs, 


. 152 


Pile, 


. 415 


Pile, Differential Thermo-electric 533 


Pile, Muscular . 


. 388 


Pile or Battery, Thermo-electric 530 


Pilot Brush, 


. 91 


Pilot Lamp, . 


. 323 


Pilot Transformer, . 


. 415 


Pilot Wires, . 


. 415 


Pistol, Electric . 


. 416 


Pith, .... 


. 416 


Pith Ball Electroscope, . 


. 234 


Pith-balls, 


. 416 


Pivoted Armature, . 


. 47 


Pivot Suspension, . 


. 416 


Plane, Magnetic Proof 


. 350 


Plant, .... 


. 417 


Plant Electricity, 


. 417 


Plant, Isolated 


. 309 


Plant's Secondary Battery, 


. 72 


Plate, Arrester 


. 417 


Plate Condenser, 


. 417 


Plate, Earth . 


. 203 


Plate Electrical Machine, 


. 417 


Plate, Franklin's . 


. 262 


Plate, Generating 


. 277 


Plate, Ground 


. 417 


Plate, Negative 


. 417 


Plate, Positive 


277-417 


Plating Balance, 


. 417 


Plating Bath, 


. 418 


Plating, Electro- 


. 418 


Platinized Carbon Battery, 


69 


Platinoid, .... 


. 418 


Platinum, 


. 419 


Platinum Alloy, 


. 419 


Platinum Black, 


. 419 


Platinum Silver Alloy, 


. 419 


Platinum Sponge, . 


. 419 


Play, End .... 


. 238 


Plow 


. 420 


Pliicker Tubes, . 


. 420 


Plug, 


. 420 


Plug Cut Out, . 


. 175 


Plug, Double . 


. 191 


Plug, Grid 


. 420 


Plug, Infinity . . 


305-420 


Plug Key, .... 


. 316 


Plug Switch, .... 


. 420 



INDEX. 



662 



Page. 
. 421 



Plumbago, 

Plunge Battery, .... 69 

Plunger, 421 

Plunger and Coil, .... 131 
Plunger and Coil, Differential 132 

Plunger, Coil and . . . .131 
Plunger Electro-magnet, t . . 220 
Pneumatic Battery, . . 69 

Pneumatic Signals, Electro- . . 231 

P.O., 421 

Pockets, Armature . . . .47 
Poggendorf's Solution, . . 421 

Point, Contact 147 

Point, Indifferent . . . .421 

Point, Neutral 421 

Point, Nodal 422 

Point, Null 422 

Point of Commutator, Neutral . 390 

Point Poles 422 

Points, Consequent . . . 422 
Points, Corresponding . . . 422 
Points, Iso-electric . 422 

Points of Derivation, . . 180-423 
Point, Thermo-electric Neutral . 390 

Polar Angle, 423 

Polar Extension, .... 423 
Polarity, Diamagnetic . . 181-423 
Polarity, Resultant . . . 470 

Polarization, 423 

Polarization, Back Electro-motive 

force of 156 

Polarization Capacity, . . . 424 
Polarization, Dielectric . . . 183 
Polarization, Galvanic . . . 265 
Polarization, Magnetic Rotary . 351 
Polarization of the Medium, . 424 
Polarized Armature, . . .47 

Polarized Electro-magnet, . . 220 
Polarized Relay, .... 458 
Polarized Relay, Tongue of . 542 

Polarizing Current, .... 164 
Polar Region, .... 424 

Polar Span, 424 

Polar Span, Angle of . . 32-423 

Polar Tips, 423 

Polar Zone, 582 

Pole, Analogous . . . 31-425 
Pole, Antilogous .... 425 
Pole, Armature . . . .47 

Pole, Austral 54 

Pole, Boreal 85 

Pole Brackets, Telegraph . . 515 

Pole Changer, 425 

Pole Changing Switch, . . 501 

Pole Dynamo, Interior . . . 199 
Pole, Magnet .... 366 

Pole, Negative ..... 425 

Pole, North 392 

Pole, North-seeking . . . .393 
Pole or End, Marked . . .368 

Pole Piece 423 

Pole Pieces, 425 



Page. 
Pole, Positive . . . . 425 

Pole, Salient 426 

Pole, Terminal 529 

290-126 
. 426 



Pole Tips, 
Pole, Traveling 
Pole, Unit Magnet 

Poles, 

Poles, Compensating 
Poles, Consequent 
Poles, Idle 
Poles, Magnetic 
Poles, Magnetic, False 
Poles of Intensity, . 
Poles of Verticity, 
Poles, Point 
Poles, Secondary . 
Poles, Secondary Magnet 
Polyphase Currents, 
Polyphote Lamp, 
Popgun, Electric . 
Porous Cell, 

Porous Cup, .... 
Porret's Phenomenon, 
Portative Power of Magnet, 
Portelectric Railroad, 
Portrait, Electric . 
Position, Energy of . 
Position Finder, 
Position, Sighted 
Positive Current, . 
Positive Direction, . 
Positive Electricity, 
Positive Element, 
Positive Feeder, 
Positive Plate, . 
Positive Pole, 
Positive Potential, . 
Positive Side of Circuit, 
Post Office, 

Posts, Binding, or Screws, . 
Potential, .... 
Potential, Absolute 
Potential, Constant . 
Potential Difference, Contact 
Potential Difference, Electric 



425 
426 

146 
296 
350 
350 
426 
426-560 

. 422 
478 
366 
167 
323 
282 

. 427 
159-426 

. 427 
366 

.427 
415 

. 241 
427 

. 484 
164 

.428 
428 

. 277 
251 

7-417 
425 

. 432 
125 

. 428 
81 

. 428 
428 

. 429 
147 
429 



Potential Difference, Electro-motive 429 
Potential, Electric Absolute . . 429 
Potential, Fall of . . . .430 
Potential Galvanometer, . . . 269 
Potential in Armature, Curve of 

Distribution of . . . . 172 
Potential, Magnetic . . 350-431 
Potential, Negative .... 432 
Potential or Static Energy, . . 241 
Potential, Positive .... 432 
Potential Regulation, Constant . 455 
Potential, Unit of Electric . . 432 
Potential, Zero . . . 432-582 

Potentiometer, 432 

Poundal, 433 

Pound-foot, 259 

Power, 433 



664 



INDEX. 



Power, Candle . 

Power, Directive . 

Power, Electric 

Power, Horse 

Power, Illuminating 

Power, Multiplying 

Power of Magnet, Portative 

Power of Periodic Current, 

Powers of Ten, . 

Power, Stray . 

Power, Thermo-electric . 

Press Button, 

Pressel, .... 

Pressure, 

Pressure, Electric 

Pressure, Electrification by 

Primary, .... 

Primary Ampere-turns, 

Primary Battery, 

Prime, .... 

Prime Conductor, 

Prime Conductor, Coatings of 

Prime Motor, .... 

Principle, Gauss' 

Printing Telegraph, 

Probe, Electric . 

Projecting Power of a Magne 

Prony Brake, 

Proof Piece, Magnetic . 

Proof-plane, . . 

Proof Plane, Magnetic 

Proof-sphere, 

Proportional Galvanometer, 

Proportionate Arms, 

Prostration, Electric 

Protector, Body 

Protector, Comb . 

Protector, Electric . 

Pull 

Pulsatory Current, . 

Pulsatory Field, 

Pulsating Motor, 

Pulvermacher's Electro - medical 

Battery, 
Pump, Geissler 
Pump, Sprengel 
Pump, Swinburne 
Pumping, .... 
Puncture-electro, . 
Puncture-galvano, 
Push Button, .... 
Push, Desk 

Push, Floor .... 
Pyro-electricity, 
Pyromagnetic Generator, 
Pyromagnetic Motor, 
Pyromagnetism, 
Pyrometer, Siemens' Electric 



Page. 
. 100 

187 
. 433 

290 



. 349 

. 366 
. 433 

. 527 
. 495 

. 533 
94 

. 434 
. 434 

. 434 
. 434 

. 434 
31-551 
69-434 
. 434 
146-434 

. 129 
. 385 

. 276 
. 515 

. 435 
. 435 

. 435 
. 350 

. 436 
. 350 

. 436 
. 269 

. 436 
. 437 

. 84 
. 437 

. 437 
. 43T 

. 164 
256 
386 



. 437 

. 439 
. 440 

. 439 

. 232 

232 

93-98-440 

. 180 
. 258 

. 441 
. 442 

. 441 
. 443 

. 443 



Quad, . 
Quadrant, 



. 443 

288-443 
288-443 



Page. 
Quadrantal Deviation, . . .180 
Quadrant, Legal .... 444 
Quadrant, Standard . . . 444 

Quadrature, 444 

Quadruplex Telegraph, . . . 515 

Qualitative 444 

Quality of Sound, .... 444 

Quantitative, 444 

Quantity, 444 

Quantity Armature, ... 47 
Quantity, Electric .... 444 
Quantity, Electro-magnetic . . 445 
Quantity, Electro-magnetic, Practi- 
cal Unit of .... 445 
Quantity, Electrostatic . . . 445 
Quantity Galvanometer, . . 269 
Quantity, Magnetic .... 350 
Quantity Meter, .... 445 

Quartz, 445 

Quicking, 446 

R, . .446 

Racing of Motors, . . • . . 446 
Radial Armature, .... 47 

Radian, 446 

Radiant Energy, .... 446 
Radiant Matter, .... 368 

Radiation, 446 

Radicals, 446 

Radiometer, 447 

Radiometer, Electric . . 447 

Radio-micrometer, . . . 447 

Radiophony, 447 

Railroad, Portelectric . . . 427 

Range Finder, 447 

Rate Governor, .... 449 
Rate Governor or Phonophone, 

Langdon Davies' . . . 450 
Rated Candle Power, . . .101 

Ratio Arms, 437 

Ratio, Core 154 

Ratio, Shunt 483 

Ratio, Velocity 560 

Ray, Electric 450 

Rayleigh Ohm, 396 

Reaction Ceil 132 

Reaction of a Dynamo Field and 

Armature, .... 450 
Reaction of Degeneration, . . 179 
Reactions, Anodic .... 36 
Reactions, Armature . . .47 
Reaction Telephone, . . . 527 
Reaction Wheel, .... 259 
Reading Galvanometer, Direct . 269 
Reading, Sound .... 489 
Reading Telescope, . . . 450 
Real Efficiency of Secondary Bat- 
tery, 205 

Real Hall Effect, .... 284 
Reaumur Scale, .... 450 

Recalescence, .... 451 

Receiver, . . . . . . 451 



INDEX. 



66.s 



Electric 



Receiver, Harmonic 
Receiver, Morse 
Receptive, Electro- 
Recharge, . 
Reciprocal, 
Reciprocating Motor 
Recoil Circuit, 
Recorder, Chemical . 
Recorder, Morse . 
Recorder, Siphon 
Record, Telephone 
Rectification of Alcohol 
Rectified Current, 
Rectilinear Current, 
Red Varnish, . 
Red Magnetism, 
Redressed Current, 
Reduced Resistance, 
Reducteur for Ammeter, 
Reducteur for Voltmeter, 
Reduction of Ores, Electric 
Reduction of Phosphorous 

trical .... 
Reflecting Galvanometer, 
Reflector, Parabolic . 
Refraction, Electric Double 
Refraction, Electrostatic 
Refreshing Action, 
Region, Extra-polar 
Region, Intrapolar 
Region, Polar 
Register, Electric . 
Register, Telegraphic 
Regulation, Constant Current 



Page. 
234-451 

. 381 
. 232 

. 115 
. 451 

. 385 
. 125 

. 117 
. 451 

. 452 
451 



18 
. 164 

. 165 
. 559 

. 357 
. 165 

. 467 
. 453 

. 453 
. 453 
Elec- 

. 410 
. 270 

. 402 
. 454 

. 235 
. 454 

. 454 
. 307 

. 424 
. 454 

. 454 
454 
455 



Regulation, Constant Potential 
Regulation of Alternating Current 

Dynamo, 195 

Regulation of Dynamos, . . 455 

Reguline, 456 

Relative, 456 

Relative Calibration, ... 98 

Relay, ...... 456 

Relay Bell, 80 

Relay Bells, 457 

Relay, Box Sounding . . . 457 
Relay Connection, . . . 457 

Relay, Differential .... 457 
Relay Magnet, .... 457 
Relay, Microphone . . . 377-457 
Relay, Neutral, Armature . . 390 
Relay, Polarized .... 457 

Reluctance, 458 

Reluctance, Magnetic . . 351-458 
Reluctance, Unit of . . . 458 

Reluctivity, 459 

Reluctivity, Magnetic . . .351 
Remanence, .... 459 

Remanence, Magnetic . . . 358 
Removal of Hair by Electrolysis, . 283 

Renovate, 115 

Repeater, 459 

Repeater, Telegraph . . . 518 



Page. 

Replenisher, Sir Wm. Thomson's . 459 

Repulsion, Magnetic . . 338 

Repulsion and Attraction, Electro- 
static 234 

Repulsion and Attraction, Electro' 
magnetic, 

Reservoir, Common 

Residual Atmosphere 

Residual Capacity, 

Residual Charge, 

Residual Magnetism, 

Residue, Electric 

Resin, 



Resinous Electricity, 
Resistance, 



Resistance, Apparent 
Resistance, Assymmetrical 
Resistance Box, 
Resistance, B. A. Unit of 
Resistance Box, Sliding . 
Resistance, Breguet Unit of 
Resistance Bridge, . 
Resistance Coil, 
Resistance Coil, Standard 
Resistance, Carbon 
Resistance, Combined 
Resistance, Compensating 
Resistance, Critical . 
Resistance, Dielectric . 
Resistance, Digney Unit of 
Resistance, Electrolytic 
Resistance, English Absolute 

Foot-second Unit of 
Resistance, Equivalent 
Resistance, Essential 
Resistance, External 
Resistance Frame, . 
Resistance, German Mile Unit of 
Resistance, Hittorfs 
Resistance, Inductive . 
Resistance, Insulation 
Resistance, Internal 
Resistance, Jacobi's Unit of . 
Resistance, Joint . . . . 
Resistance, Magnetic 
Resistance, Matthiessen's 

gram Standard of 



217 

460 

460 

. 103 

. 116 
. 358 
116-460 
. 460 

. 461 
. 461 
297-462 
. 462 

. 462 
. 462 

. 463 
. 463 

. 577 
. 137 

. 464 
. 463 

. 464 
. 144 

. 464 
183-464 

. 464 
. 464 



or 



465 

465 

, 465 

465 

465 

466 

466 

. 466 

\ 466 

. 466 

. 466 

. 464 

. 351-458 

Meter- 

. 466 
Resistance, Matthiessen's Unit of 466 
Resistance, Meter-millimeter Unit 

of 466 

Resistance, Mil-foot Unit of . .467 
Resistance, Non-essential . 465-467 
Resistance, Non-inductive . . 467 
Resistance of Human Body . . 467 
Resistance, Ohmic . . . 394-467 
Resistance, Reduced . . . 467 
Resistance, Siemens' Unit of . . 467 
Resistance, Specific . . . 467 
Resistance, Specific Conduction . 467 
Resistance, Spurious . . . 467 
Resistance, Steadying . . . 468 
Resistance, Swiss' Unit of . . 468 



666 



INDEX. 



Resistance, Thomson's Unit o 

Resistance to Sparking, 

Resistance, True 

Resistance, Unit . 

Resistance, Unit of, B. A. 

Resistance, Varley's 

Resistance, Varley's Unit of 

Resistance, Virtual 

Resistance, Weber's Absolute 

Resolution of Forces, 

Resonator, Electric 

Rest, Currents of 

Resultant, 

Resultant Polarity, . 

Retardation, . 

Retardation of Phase, 

Retentivity, . 

Retentivity, Magnetic 

Retort Carbon, 

Return, 

Return Circuit, 

Return, Earth . 

Return Stroke, 

Reversal, Therrao-Electric 

Reverse Current Working, 

Reverse-induced Current, 

Reverser, Current 

Reversibility, 

Reversible Bridge, 

Reversing Key, 

Reversing Switch, 

Revivify, . 

Revolving Armature 

Rheochord, 

Rheometer, 

Rheomotor, 

Rheophore, 

Rheoscope, 

Rheoscopic Frog 

Rheostat, . 

Rheostat Arm, 

Rheostatic Machine, 

Rheostat, Wheatstone's 

Rheotome, . 

Rheotrope, 

Rhigolene, 

Rhumbs, . . 

Rhumkorff Coil, 

Ribbon Coil, . 

Ribbon Core, 

Right-handed Screw 

Rigidity, Molecular 

Ring, Ampere 

Ring Armature, 

Ring, Collecting . 

Ring Contact, . 

Ring Core, 

Ring, Dynamo . 

Ring, Faraday's 

Ring, Foundation 

Ring, Guard . 

Ring, Pacinctti's 



Page' 



Law 



Page. 

. 468 
. 490 

. 467 
. 468 

. 78 
. 559 

. 468 

297 

Unit 468 

. 261 
468-470 

. 167 
. 470 

. 470 
. 470 

. 471 
. 471 

. 351 
. 471 

. 471 
. 125 

. 203 
55 

. 533 
. 581 

. 163 
. 165 

. 471 
. 472 

. 316 
. 501 

. 115 
47 

. 472 
. 472 

. 472 
. 472 

. 472 
. 262 

. 472 
. 472 

. 172 
. 472 

. 473 
. 473 

. 473 
. 473 
138-473 
. 138 

. 154 

. 324 

380-473 

30 

. 48 
. 139 

. 473 
. 155 

. 200 
. 473 

. 261 
. 282 

. 400 



Page. 
Rings, Electric . . . 'd& 

Rings, Nobili's 392 

Ring, Split, Commutator . . 141 
Roaring, ...... 474 

Rocker, 474 

Rocker Arms, .... 50-474 

Rod, Bus 94 

Rod, Discharging .... 189 
Rod, Omnibus .... 94 

Roget's Spiral, 474 

Rolling Armature, ... 49 

Rosin, 460 

Rotary Polarization, Magnetic . 351 
Rotating Brush, .... 91 
Rotating Field, . . . .256 
Rotation of Liquids, Electro-dynamic 474 
Rotation of Liquids, Electro-mag- 
netic 475 

Rotatory Currents, . . . 167 

Rubber, 102-475 

Rubber, India . . . . 102 

Saddle Bracket, .... 475 

Safety Catch 175 

Safety Cut Out, .... 175 
Safety Device, . . . . . 475 

Safety Fuse 175-475 

Safety Fuse, Plug, or Strip . . 475 
Sal Ammoniac Battery, . . 69 

Salient Pole, 426 

Salt, . ■ 475 

Salt, Dronier's 192 

Salt or Sea-salt Battery, . . 69 

Sand Battery, 90 

Saturated, 476 

Saturation, Magnetic . . . 351 
Saw, Electric . 476 

Scale, Fahrenheit .... 248 
Scale, Reaumur .... 450 

Scale, Tangent 502 

Schweigger's Multiplier, . . 476 
Scratch Brushes, .... 476 
Screen, Electric .... 476 
Screen, Magnetic .... 351 
Screen, Methven .... 376 
Screws or Posts, Binding . . 81 

Sealed, Hermetically . . .289 
Sea Salt or Salt Battery, . . . 69 

Secohm, 288 

Second, Ampere- . . . .30 
Secondary Actions, . . . 477 
Secondary Ampere-turns, . 31-551 

Secondary Battery, ... 70 
Secondary Battery, Efficiency of, 

Quantity 205 

Secondary Battery, Plante's . 72 
Secondary Clock, .... 127 
Secondary Current, . . .166 
Secondary Generator, . . 277-477 
Secondary Magnet Poles, . . 366 
Secondary, Movable . . . 477 

Secondary Plates, Colors of . 478 



INDEX. 



667 



Page. 
Secondary Poles, . . . .478 
Secretion Current, . . . 166 

Section Trolley, . . . .549 

Sectioned Coils, .... 138 
Seebeck Effect, . . . .478 

Segments, 56 

Segments, Commutator . . .56 

Selenium, 478 

Selenium Cell, 478 

Selenium Eye, .... 478 
Self-exciting Dynamo, . . . 201 
Self-induction, .... 303 
Self-induction, Magnetic . . 352 

Self-induction, Unit of . . . 304 

Self-repulsion, 478 

Self-winding Electric Clock, . 128 
Semi-circular Deviation, . . . 181 
Semi-conductors, .... 478 
Semi-incandescent Lamp, . . 323 

Sender, Zinc 582 

Sensibility, 479 

Sensitiveness, Angle of Maximum 479 
Separate Circuit Dynamo, . . 201 
Separate Touch, . . . 359-479 
Separate Touch, Magnetization by 359 
Separately Excited Dynamo, 201-479 
Separation of Electricities, . . 479 

Separator, 479 

Separator, Magnetic . . . 352 

Series, 479 

Series and Long Shunt Winding, . 579 
Series and Separate Coil Winding, 579 
Series and Short Shunt Winding, 580 
Series, Contact 147 



Series Dynamo, 

Series, Electro-chemical , 

Series, Electro motive . 

Series, Electrostatic 

Series Motor, . 

Series, Multiple- 

Series-multiple, 

Series, Thermo-electric 

Series Transformer, 

Series Winding, 

Service Conductors, 

Serving, 

Shackle, .... 

Shadow, Electric 

Shadow, Molecular 

Shadow Photometer, 

Sheath for Magnet Coils, 

Sheath for Transformers, 

Sheath, Induction . 

Sheet Current, . 

Shell, Magnetic 

Shell, Strength of Magnetic, 

Shellac, . 

Shellac Varnish, 

Shield, Anti-magnetic 

Shield, Magnetic 

Shielded, 

S. H. M., . 



201 
. 209 

228 
. 235 

386 
. 387 

480 
. 534 

548 
. 579 

480 



Page. 
Shock, Back, or Stroke of Lightning 55 
Shock, Break 482 



480 



480 
414 
481 
481 
303 
166 
352 
35C 
481 
481 
37 
351-353 
481 
482 



Shock, Electric 


. 482 


Shock, Opening 


. 482 


Shock, Static . 


. 482 


Short Circuit, 


. 482 


Short Circuit Working, 


. 482 


Short Fall Air Pumps, 


. 16 


Short Shunt Winding . 


. 579 


Shovel Electrodes, . 


. 483 


Shower Bath, Electric . 


5T 


Shunt, .... 


. 483 


Shunt Box, 


. 483 


Shunt Circuit, . 


. 123-126 


Shunt Dynamo, 


. 202 


Shunt, Electro-magnetic . 


. 483 


Shunt, Galvanometer . 


271-483 


Shunt, Magnetic 


. 353 


Shunt Motor, . 


. 386 


Shunt. Multiplying Power 


i a . 388 


Shunt Ratio, . 


. 483 


Shunt Winding , 


. 580 


Shuttle Armature, 


49 


Shuttle Current, 


. 483 


Shuttle Winding, . 


483-580 


Side Flash, 


. 484 


Siemens and Halske's Battel 


T, • 72 


Siemens' Differential Voltan 


leter, . 564 


Siemens' Electro-dynamome 


ter, . 212 


Siemens' Old Armature, . 


. 49 


Siemens' Unit of Resistance 


. 467 


Sighted Position, 


. 484 


Signaling, Velocity of . 
Signals, Electro-pneumatic 


. 560 


. 231 


Signal, Telegraph . 
Silent Discharge, 


. 519 


187-189-206 


Silver, .... 


. 484 


Silver Bath, ... 


. 484 


Silver, German 


. 277 


Silver Stripping Bath, 


. 484 


Silver Voltameter, . 


. 565 


Simple Arc, 


. 39 


Simple Circuit, 


. 126 


Simple Harmonic Motion, 


. 486 


Simple Immersion, 


. 185 


Simple Magnet, 


. 366 


Simple Substitution, 


. 485 


Sims-Edison Torpedo, 


. 543 


Sine Curve, 


174-485 


Sine Galvanometer, . 


. 271 


Sine Law, 


. 486 


Sines, Curve of 


. 173-485 


Single Coil Dynamo, 


. 202 


Single Curb Working, 


. 581 


Single Fluid Theory, 


. 486 


Single Fluid Voltaic Cell, 


. 486 


Single Needle Telegraph, 


. 519 


Single Touch, Magnetizatior 


1 by . 359 


Sinistrotorsal, . 


. 486 


Sinuous Current, 


. 166 


Sinusoidal Curve, . 


174-485 


Siphon Recorder, 


. 452 



668 



INDEX. 



Sir William Thomson's Battery, 
Skin Effect, . 
Skrivanow Battery, . 

Sled 

Sleeve. Joint 
Slide, Balance 
Slide Bridge, 
Slide Meter Bridge, 
Sliding Condenser, . 
Sliding-contact Key, 
Sliding Resistance Box, 
Slope, Lines of 
Smee's Battery, 
S. N. Code, . 
Snap Switch, 
Soaking-in-and-out, 
Socket, Lamp 
Socket, Wall . 
Soldering, Electric . 
Solenoid, 
Solenoid Ammeter, 



Solenoidal Distribution of Magnet- 



Acid 



ism, .... 
Solenoidal Magnet, 
Solid Earth, 

Solutions, Battery, Chromic 
Solution, Chutaux's 
Solution, Delaurier's 
Solution, Hittorf's 
Solution, Kookogev's 
Solution, Poggendorf's . 
Solution, Striking 
Solution, Tissandier's . 
Solution, Trouve's . 
Sonometer, Hughes 1 
Sonorescence, 
Sound, Characteristics of 
Sounder, .... 
Sounders, Tin 
Sound, Quality of 
Sound Reading, 
South Magnetic Fluid, 
Space, Clearance 
Space, Crookes 1 Dark 
Space, Dark, Faraday's 
Space, Faraday's Dark 
Space, Inter-air 
Space, Interferric 
Span, Polar 
Span, Polar, Angle 
Spark Arrester, 
Spark Coil, 
Spark Discharge, 
Spark, Duration of 
Spark Gap, 
Spark. Length of 
Spark Micrometer, 
Spark Tube, 
Sparking, 
Sparking Distance, 
Sparking, Lines or Points of Least 
Sparking, Resistance to 



of the 



Electric 



Page. 
. 72 

486 
. 72 

486 
. 310 

374 
. 374 



. 144 
316 

. 463 

330 

. 73 

486 
. 501 

486 
. 323 

572 

. 487 

487 

28 



358 
366 
203 
73 
119 
179 
289 
318 
421 
496 
542 
549 



114 



542 
444 

489 
356 

489 

489 

249-489 

249-489 



424 
32 



490 
490 
490 
470 
491 
490 
190 
490 
. 490 



Page. 
Specific Conduction Resistance, . 467 
Specific Conductivity, . . . 145 

Specific Heat 286 

Specific Heat of Electricity, . .491 
Specific Inductive Capacity, . 103 
Specific Magnetization, . . . 361 
Specific Resistance, . . . 467 
Speech, Articulate . . . .50 
Speed, Critical .... 157 

Spent Acid, 491 

Spent Liquor, .... 491 

Spherical Armature, . . .49 

Spherical Candle Power, . . 101 
Spherical Illuminating Power, . 296 
Sphygmophone, .... 491 
Sphygmophone, Electric . . . 491 

Spiders, 491 

Spiral 492 

Spiral Battery, .... 73 
Spiral, Roget's . . . .474 

Spiral Winding, .... 492 
Spirit Compass, .... 143 

Splayed Joint, . . . .311 

Splice Box, 492 

Split Battery, 73 

Split Ring Commutator, . . . 141 

Spluttering, 492 

Sponge, Platinum . . . .419 

Spot, Grease 92 

Sprengel Pump, .... 439 

Spring Ammeter, .... 28 
Spring and Fibre Suspension, . 252 
Spring-contact, .... 148 

Spring Control, 492 

Spring Jack Cut-out, . . . 493 
Spurious Hall Effect, . . .284 
Spurious Resistance, . . . 467 
Spurious Voltage, .... 493 

Square Mil, 379 

Square Wire, 493 

Squares, Law of Inverse . . 323 
St. Elmo's Fire, . . . .494 

Staggering, 493 

Standard Candle, . . . .101 
Standard Candle, German . . 99 
Standard, Harcourt's Pentane . 406 
Standard, Methven . . .376 
Standard of Illuminating Power, 

Viole's 561 

Standard or Main Feeder, . . 251 
Standard Quadrant, . . . 444 
Standard Resistance Coil, . . 464 
Standard Voltaic Cell, . . .109 
Standard Voltaic Cell, DanielFs . 109 
Standard Voltaic Cell, Latimer 

Clark's 110 

State, Electrotonic . . . 493 

State, Nascent 389 

State of Matter, Fourth . . 261 

State, Passive 404 

State, Permanent . . . .408 
Static Breeze, 493 



IXDEX. 



Static Condenser, Armature of 
Static Electricity, 
Static Hysteresis, . 
Static Induction. Magnetic 

Static Shock 

Station, Central 
Station, Distant 
Station, Home . 

Station, Transforming . 
Steadying Resistance, 

Steel, 

Steeling 

Steel Yard Ammeter, . 
Step-by-step Telegraph, . 
Step-by-step Telegraphy, 
Step-down, . 

Step, Foot- . ... 

Sticking 

Stool, Insulating . 

Stopped Coil Electro-magnets, 

Stopping Off, .... 

Storage Battery, 

Storage Battery Changing Swi 

Storage Battery, Planters 

Storage Capacity, . 

Storage of Electricity, 

Storms, Electric 

Storms, Magnetic 

Strain, . ... 

Strain, Dielectric 

Strain, Magnetic . 

Stranded Conductor Armature 

Stranded Core, 

Stray Field, . 

Stray Power, .... 

Streamlets, Current . 

Strength, Dielectric 

Strength of Magnetic Shell, . 

Stress, 

Stress, Dielectric 
Stress. Electro-magnetic 
Stress. Electrostatic . 
Stress, Energy of . 
Stress. Magnetic . . 
Striae. Electric 
Striking Distance, 
Striking Solution, . 

Stripping 

Stripping Bath, 

Stripping Bath. Gold 

Stripping Bath, -Silver . 

Stroke, Back . 

Stroke or Shock of Lightning, 

Stroke, Return . 

Sub-branch 

Sub-main 

Sub-permanent Magnetism, 
Substitution, Simple 
Subway, Electric . 
Successive Temperatures, Law 
Sucking Coil, .... 
Sucking Magnet, . . 



Page. 

46 

. 493 

. 295 

. 347 

. 482 

. 493 

. 493 

. 493 

. 494 

. 468 

. 494 

. 494 

28 

. 506 

. 494 

. 494 

. 259 

. 494 

. 305 

. 221 

. 495 

TO 

501 

72 

105-495 

. 495 

495 

353 

495 

183 

354 

48 

155 

256-495 

495 

495 

183 

352 

495 

496 

219-496 

236-496 

241 

854 

496 

496 



tch, 



496 
496 
358 
485 
496 
324 
132 
366 



Sulphate of Lead Battery, . . 66 
Sulphate of Mercury Battery, . 67 

Sulphating, 49? 

Sulphur Dioxide, .... 497 



496 



279 

4S4 



Back 55 



Sulphuric Acid, 


. 497 


Sulphuric Acid Voltameter, 


. 564 


Sulphurous Acid Gas, . 


. 497 


Sunstroke, Electric . 


. 497 


Superficial Density, Electric 


. 180 


Supersaturated, 


. 497 


Supply, Isolated 


. 309 


Surface, 


. 497 


Surface Density, . 


. 498 


Surface, Equipotential 


. 498 


Surface Leakage, . 


. 498 


Surface Magnetization, 


. 356 


Surgical Electro-magnet, 


. 222 


Surging Discharge, . 


. 188 


Surveyors' Compass, 


. 143 


Susceptibility, Magnetic . 


354-359 


Suspension, .... 


. 49S 


Suspension. Bifilar . 


. 498 


Suspension, Fibre 


. 252 


Suspension, Knife Edge . 


. 317 


Suspension, Pivot . 


. 416 


Suspension, Spring and Fibre 


. 252 


Suspension, Torsion 


. 545 


Suspension Wire of Cable, 


. 97 


Swaging. Electric 


. 499 


Swelling Current, 


. 167 


S. W. G„ .... 


. 499 


Swinburne Pump. 


, 440 


Swinging Earth. . 


. 203 


Swinging or Pendulum Annuncia- 


tor 


35 


Swiss Unit of Resistance 


. 468 


Switch, 


. 499 


Switch. Automatic . 


. 500 


Switch Board. 


. 500 


Switch Board, Multiple , 


. 387 


Switch Board, Trunking 


. 550 


Switch, Break-down 


. 88 


Switch, Changing . 


. 500 


Ssvitch, Changing Over . 


. 500 


Switch, Circuit Changing 


. 500 


Switch, Double Break 


. 500 


Switch, Double Pole 


. 500 


Switch Feeder, . . . 


. 500 


Switch, Knife 


. 501 


Switch, Knife Break 


. 501 


Switch, Knife Edge 


. 501 


Switch, Multiple 


. 501 


Switch, Plug .... 


. 420 


Switch. Pole Changing . 


. 501 


Switch, Reversing 


. 501 


Switch, Snap .... 


. 501 


Switch, Storage Batterv Chang 


ing 501 


Switch, Three Way 


. 501 


Switches, Distributing 


. 190 


Symmer's Theory . 


191 


Sympathetic Vibration, . 


501-561 


System, Block 


83 



670 



INDEX. 



System of Co-ordinates, 
System, Tower 



X, ..... . 

Tailing Current, 
Tailings, .... 

Talk, Cross 

Tamidine, .... 
Tangent Galvanometer, . 
Tangent Law, 
Tangent Positions of, Gauss 
Tangent Scale, 
Tangentially Laminated Core 
Tank, Cable .... 
Tape, Insulating 
Tapper Key, Double . 
Teazer, 

Technica, Memoria, Ampere's 
Tee, Lead .... 
Teeth, Pacinotti . 
Tel-autograph, . 
Tele-barometer, Electric 
Telegraph, A. B. C. . 
Telegraph, Autographic 
Telegraph, Automatic 
Telegraph, Dial 
Telegraph, Double Needle 
Telegraph, Duplex 
Telegraph, Duplex, Bridge 
Telegraph, Duplex, Differential 
Telegraph Embosser, 
Telegraph, Facsimile . 
Telegraph, Harmonic Multiplex 
Telegraph, Hughes' 
Telegraph Insulator, 
Telegraph Key, 
Telegraph, Magneto-electric 
Telegraph, Morse . 
Telegraph, Multiplex 
Telegraph, Single Needle 
Telegraph, Overhouse 
Telegraph Pole Brackets, 
Telegraph, Printing 
Telegraph, Quadruplex 
Telegraph Repeater, 
Telegraph Signal, . . . 
Telegraph, Step-by-step . 
Telegraph, Wheatstone's, A 
Telegraph, Writing . 
Telegraphic Alphabet, . 
Telegraphic Code, 
Telegraphic Needle, 
Telegraphic Register, 
Telegraphy, Multiplex . 
Telegraphy, Step-by-step 
Telemanometer, Electric 
Telemeter, Electric . 
Telepherage, .... 
Telephone, 
Telephone, Bi- 
Telephone, Capillary 
Telephone, Carbon 



Page. 

. 150 

545 



501 
. 501 

501 
. 158 

502 
. 272 

502 
. 276 

502 

. 155 

97 

. 305 

314 

. 504 

30 

. 504 

400 
. 504 

504 
. 504 

510 
. 504 

505 
. 506 

506 
. 506 

507 
. 237 

510 
. 510 

511 
. 306 

316 
. 512 

512 
. 514 

519 
. 515 

515 
. 515 

515 
. 518 

519 

. 506 

. 521 

. 521 

19 

130-511 

389 

454 



. 494 

521 
. 521 

522 
. 522 

524 
. 525 

525 



Page. 
Telephone, Chemical . . . 526 
Telephone, Electrostatic . . 526 
Telephone Exchange, . . . 246 
Telephone Induction Coil, . 137-526 
Telephone, Reaction . . . 527 
Telephone Record, . . . 451 
Telephone, Thermo-electric . . 527 
Telephone Tinnitus, . . . 542 
Telephotography, .... 521 

Telephote 527 

Telescope, Reading .... 450 

Teleseme 527 

Tele-thermometer, .... 527 

Terminal, 529 

Terminal Pole, 529 

Terminal Voltage, . . .562 
Temperature, Absolute ... 8 
Temperature, Neutral . . . 390 
Temperatures, Laws of Successive 324 
Tempering, Electric . . . 527 
Temporary Magnetism or Magneti- 
zation, 357 

Ten, Powers of 527 

529 
. 189 

529 
. 358 

529 
. 581 

529 
. 148 

191 



Tension, 

Tension, Disruptive . 

Tension, Electric . 

Terrestrial Magnetism 

Tetanus, Acoustic 

Tetrode Working, 

Theatrophone, 

Theory, Contact 

Theory, Double Fluid 

Theory, Franklin's . 

Theory of Dimensions, . . 184 

Theory of Light, Electro-magnetic 219 

Theory of Light, Maxwell's . 369 

Theory of Magnetism, Ampere's . 354 

Theory of Magnetism, Ewing's . 356 

Theory of Magnetism, Hughes' . 357 

Theory of Magnetism, Weber's . 358 

Theory, Symmer's .... 191 

Therapeutic Electrode, . . 210 

Therapeutics, Electro- . . .236 

Therm 529 

Thermaesthesiometer, . . . 530 

Thermal Electric Meter, . . 375 

Thermal Equivalent, Electro- . 245 

Thermal Energy 242 

Thermic Balance, . . . .85 

Thermo Call 530 

Thermo-chemical Battery, . . 530 

Thermo-chemical Equivalent, . 245 

Thermo-electric Battery or Pile, . 530 

Thermo-electric Call, . . . 531 

Thermo-electric Couple, . . . 532 

Thermo-electric Current, . . 167 

Thermo-electric Diagram, . . 532 

Thermo-electric Element, . . 237 

Thermo-electric Inversion, . . 533 

Thermo-electric Junction, . . 533 

Thermo-electric Neutral Point . 390 

Thermo-electric Pile, Differential 533 



INDEX. 



6/i 



Page. 
Thermo-electric Power, . . .533 
Thermo-electric Reversal, . . 533 
Thermo-electric Series, . . . 534 
Thermo-electric Telephone, . 527 

Thermo-electric Thermometer, . 535 
Thermo-electricity, . . . 533 
Thermo-electricity, Laws of, Bec- 

querel's 78 

Thermo-electricity, Volta's Law of 568 
Thermo-electrometer. . . . 536 

Thermolysis, 535 

Thermo-multiplier, . . . 536 

Thermometer, 535 

Thermometer, Electric . . 535 

Thermometer, Kinnersley's . . 536 
Thermometer, Tele- . .527 

Thermometer, Thermo-electric . 535 
Thermophone, .... 537 
Thermostat, Electric . . . 537 

Third Brush 91 

Thomson Effect, .... 538 
Thomso'n's Replenisher, SirWilliam 459 
Thomson's Battery, Sir William . 72 
Thomson's Unit of Resistance, . 408 
Three Filament Incandescent 

Lamp, 322 

Three Way Switch 501 

Three Wire System, . . . 539 

Throw, 237-540 

Throw-back Indicator, . . 540 

Thrust Bearings, .... 540 

Thunder, 540 

Ticker, 540 

Tick, Magnetic .... 354 

Timbre 444 

Time Constant, .... 541 

Time Cut-outs 541 

Time Electric Meter, . . . 375 

Time-fall, 541 

Time-reaction, .... 541 

Time-rise, 541 

Tin, 541 

Tin Sounders, 542 

Tinnitus, Telephone . . . 542 

Tips, Polar 423 

Tips, Pole .... 290-426 
Tissandier's Solution, . . .542 
Toeppler-Holtz Machine, . . 334 
Tongs, Cable Hanger . . .97 
Tongs, Discharging . . . 189 
Tongue of Polarized Relay, . . 542 
Tongue of Polarized Relay, Bias of 542 
Toothed Core-discs, .... 154 
Top, Magnetic . . . . 542 
Torpedo, Electric .... 543 
Torpedo, Sims-Edison . . . 543 

Torque, 543 

Torque, Curve of . . . .174 
Torricellian Vacuum, . . . 557 
Torsion Balance, Coulomb's . 544 
Torsion Galvanometer, . . 273-544 
Torsion Head, .... 544 



Page. 
Torsion Suspension, . „ . 545 

Total Earth 203 

Touch, 545 

Touch, Separate .... 479 

Tourmaline, 545 

Tower, Electric .... 545 

Tower System 545 

Trailing Horns, .... 259 

Transformer 545 

Transformer, Commuting . . 547 
Transformer, Continuous Alternat- 
ing 547 

Transformer, Continuous Current 

384-547 
Transformer, Core . . . 547 

Transformer, Faraday's . . . 250 
Transformer, Hedgehog . . 548 
Transformer, Multiple . . . 548 
Transformer, Oil . . . . 548 
Transformer, Pilot .... 415 
Transformer, Series . . . 548 
Transformer. Sheath for . . . 481 
! Transforming Station . . 494 

! Transformer, Welding . . 548-575 

Translator, 519 

Translucent Disc Photometer, . 412 

Transmitter, . . . . . 548 
Transmitter, Carbon . . 549 

Transmission of Energy, Electric 240 

Transposing, 549 

Transverse Electro-motive Force, 549 

Trap, Bug 92 

Traveling Pole, .... 426 
Trembling Bell, . . . .78 

Trolley, 549 

Trolley, Double 549 

Trolley Section, .... 549 

Trough Battery 73 

Trouve's Blotting Paper Battery, 73 

Trouve's Solution 549 

True Contact Force, . . . 549 

True Ohm 396 

True Resistance 467 

Trimmer, Brush .... 549 
Trumpet, Electric . . . 550 

Trunk Lines 550 

Trunking Switch Board, . . 550 

Tube, Electric, 550 

Tube, Guard 282 

Tube, Luminous .... 550 
Tube of Magnetic Induction, . 347 

Tube, Spark 491 

Tube, Stratification . . . 495 
Tubes, Geissler . . . .276 

Tubes of Force .... 261 

Tubes, Plucker 420 

Tubular Braid, .... 550 

Tubular Core, 155 

Tubular Magnet, . . . .356 
Tuning Fork Circuit Breaker, . 121 
Tuning Fork Dynamo, . . 202 

Tuning Fork, Interrupter for . . 307 



672 



INDEX. 



Turning Moment, . 
Turns, .... 

Turns, Ampere- 
Turns, Dead, of a Dynamo 
Turns, Primary Ampere- 
Turns, Secondary Ampere- 
Twist Joint, American . 
Twist, Magnetic 
Tyer's Battery, 
Typewriter, Electric 
Type Printer, Hughes' 



50-; 
202- 



Ultra-gaseous Matter, . 

Unbuilding, .... 

Underground Conductor, 

Underground Electric Subway 

Undulatory, .... 

Undulatory Current, 

Unidirectional, 

Uniform Field, .... 

Uniform Field of Force, 

Uniform Magnetic Field, 

Unipolar, .... 

Unipolar Armature, . 

Unipolar Current Induction, 

Unipolar Dynamo, . . . 

Unipolar Electric Bath, 

Unipolar Induction, 

Unipolar Magnet, 

Unit 

Unit, Absolute 

Unit Angle, .... 

Unit, B. A 

Unit, B. A., of Resistance 

Unit Current, 

Unit Electro-motive Force, 

Unit, Fundamental 

Unit Jar, 

Unit Magnet Pole, 

Unit of Capacity, 

Unit of Conductivity, . 

Unit of Electric Potential, 

Unit of Energy, Electro-magnetic 

Unit of Force, .... 

Unit of Illumination, . 

Unit of Output, 

Unit of Reluctance, 

Unit of Resistance, B. A. 

Unit of Resistance, Breguet 

Unit of Resistance, Digney 

Unit of Resistance, English Abso- 
lute or Foot-second 

Unit of Resistance, German Mile 

Unit of Resistance, Jacobi's . 

Unit of Resistance, Meter-milli 
meter 

Unit of Resistance, Mil-foot 

Unit of Resistance, Siemens' . 

Unit of Resistance, Swiss 

Unit of Resistance, Thomson's 

Unit of Resistance, Varley's 

Unit of Self-induction, 



Page. 

544 

. 550 

31 

. 551 

551 

. 551 

309 

. 354 

74 

. 551 

511 



551 
552 
552 
552 

23 
167 
553 
256 
553 
345 
553 
•553 
553 
553 

57 
304 
356 
553 
554 
554 
554 
462 
167 
228 
554 
554 
366 
105 
145 
432 
220 
261 
296 
399 
458 

78 
463 
464 

. 465 



467 
467 
468 
468 



Unit of Supply, 
Unit of Work, . 
Unit Resistance, . 
Units, Circular . 
Units, Derived 
Units, Heat 
Units, Practical 
Universal Battery System, 
Universal Discharger, . 
Unmarked End, 
Upright Galvanometer, 
Upward's Battery, . 



V, 

V, A 

Vacuum, .... 

Vacuum, Absolute . 
Vacuum, High 
Vacuum Lightning Arrester, 
Vacuum, Low 
Vacuum, Partial 
Vacuum, Torricellian . 
Valency, .... 
Valve, Electrically Controlled 
Vapor Globe, 
Variable Conductivity, 
Variable Period, 
Variable State, 
Variation of the Compass, 
Variations, Magnetic . 
Variometer, 
Varley's Battery, . 
Varley's Condenser, . 
Varley's Resistance, 
Varley's Unit of Resistance, 

Varnish, 

Varnish, Electric 
Varnish, Insulating 
Varnish, Red 
Varnish, Shellac 

Vat 

Velocity, .... 

Velocity, Angular 
Velocity of Signaling, . 
Velocity Ratio, . 
Ventilation of Armature, 
Vertical Galvanometer, . 
Vertical Induction, 
Verticity, Poles of 
Vibrating Bell, 
Vibration Period, 
Vibration, Sympathetic 
Vibrator, Electro-magnetic 
Villari's Critical Value, 

Viole 

Viole's Standard of Illuminating 

Power, 
Virtual Resistance, 
Viscous Hysteresis, . 
Vis Viva, 

Vitreous Electricity, 
Vitriol, Blue . 



INDEX, 



673 



Page. 

Vitriol, Green 562 

Vitriol, White .... 562 
Volatilization of Carbon, . . 108 

Volt, 562 

Volt-ampere, 573 

Volt and Ampere Meter Galvan- 
ometer, . . . . . 274 

Volt, B. A 568 

Volt, Congress 568 

Volt, Coulomb . . . 568-573 

Volt Indicator, 568 

Volt, Legal 568 

Voltage, . . . . . .562 

Voltage, Spurious .... 493 

Voltage, Terminal .... 562 

Voltaic, 563 

Voltaic Alternatives, . . . 563 

Voltaic Arc, 39 

Voltaic Cell, Daniell's Standard . 109 
Voltaic Cell, Double Fluid . . 191 
Voltaic Cell, Capacity of Polariza- 
tion of a 103 

Voltaic Cell, Single Fluid . . 486 
Voltaic Cell, Standard . . .109 
Voltaic Cell, Standard, Latimer 

Clark's 110 

Voltaic Circuit, .... 126 

Voltaic Effect, . .563 

Voltaic Electricity, .... 563 
Voltaic Element, .... 237 
Voltaic or Galvanic Battery, . . 76 
Voltaic or Galvanic Circle . . 119 
Voltaic or Galvanic Couple, . . 156 

Voltameter, 563 

Voltameter, Copper .... 563 
Voltameter, Differential, Siemens' 564 
Voltameter, Faraday's . . . 250 
Voltameter, Gas .... 564 
Voltameter, Silver . . .565 

Voltameter, Sulphuric Acid . . 564 
Voltameter, Volume . . . 564 
Voltameter, Weight . . . . 566 
Voltametric Law, .... 567 
Volta's Battery, . . . .76 

Volta's Fundamental Experiments 567 
Volta's Law of Galvanic Action, . 568 
Volta's Law of Thermo-electricity 568 

Voltmeter, 568 

Voltmeter, Battery . . .569 
Voltmeter, Cardew . . . .569 

Voltmeter, Electrostatic . . 571 
Voltmeter, Reducteur for . . 453 
Volts, Lost ... . . .571 

Volume Voltameter, . . . 564 
Vulcanite, 571 

W., . 572 

Wall Bracket, 572 

Wall Socket, ..... 572 
Ward, . . . . . .572 

Waste Field, 256 

Water, 572 



Page. 

Water Battery 77 

Water Equivalent, .... 572 
Water Level Alarm, ... 18 
Waterproof Lamp Globe, . . 572 

Wattless Current 168 

Watt, 572 

Watt-hour 573 

Watt Meter 375 

W T att-minute, 573 

Watt-second 573 

Watts, Apparent .... 573 
Wave Winding, . . . .580 

Waves, Amplitude of . . . 31 
Waves. Electro-magnetic . . 573 

Wax, Paraffine .... 402 

Weber, 574 

Weber's Absolute Unit Resistance, 468 

Weber-meter, 574 

Weber's Theory of Magnetism, . 358 
Wedge Cut-out, . . . .175 

Wedge, Double . 191 

Weight, Atomic . . . .53 

Weight, Breaking .... 89 
Weight Electrometer. r . . 223 
Weight Voltameter, . .566 

Welding, Electric .... 574 
Welding Transformer, . . 548-575 
Wheatstone's A. B. C. Telegraph, 521 
Wheatstone's Balance, . . . 577 
Wheatstone's Bridge, . . . 575 
Wheatstone's Bridge, Commercial 86 
Wheatstone's Rheostat . . . 472 
Wheel, Phonic .... 409 
Wheel, Reaction . . . .259 
Whirl, Electric .... 577 

White Vitriol 562 

Wilde Candle 101 

Wimshurst Electric Machine, 335-577 
Wimshurst Machine, . . 335-577 

Wind, Electric 578 

W T indage, 578 

Windings, Ampere . . . .31 
Winding, Bifilar .... 81 
Winding, Compound . . . 578 
Winding, Disc .... 579 

Winding, Lap 579 

Winding, Long Shunt . . . 579 
Winding, Long Shunt and Series . 579 
Winding, Multiple . . . 579 

Winding, Multipolar . . . 579 
Winding, Series .... 579 
Winding, Series and Separate Coil 579 
Winding, Series and Short Shunt 580 
Winding, Short Shunt . . . 579 
Winding, Shunt . . . 483-580 
Winding Shuttle, . . . .580 
Winding, Wave . . . .580 
Winding Working, Differential, . 183 

Wire, Block 83 

Wire, Bus 94 

Wire, Dead 177 

Wire Finder, . . . . . . 580 



674 



INDEX. 



Wire Gauze Brush, 
Wire, Idle . 
Wire, Neutral 
Wire, Omnibus 
Wire, Square . 
Wire System, Three 
Wires, Crossing- 
Wires, Leading-in 
Wires, Phantom 
Wires, Pilot 
Wollaston Battery, 
Work, 

Work, Electric, Unit of 
Work, Unit of . 
Working - , Contraplex 
Working, Diode 
Working, Diplex . 
Working, Double Curb 
Working, Hexode . 
Working, Pentode . 



Page. 

92 

. 296 

390 
. 94 

493 
. 539 

158 
. 324 

409 
. 415 



580 
580 
581 
580 
580 
580 
581 
581 
581 



Working, Reverse Current 
Working, Single Curb 
Working Tetrode, 
Writing Telegraph, . 

X, Axis of 



V, Axis of 
Yoke, . 



^amboni's Dry Pile, 

Zero, 

Zero, Absolute . 

Zero Potential, 

Zero, Thermometric 

Zinc, 

Zinc Sender, 

Ziricode, . 

Zone, Peripolar 

Zone, Polar . 



Page. 
. 581 

. 581 
. 581 

. 521 



54 



54-397 
. 581 



. 581 
. 581 

. 581 
432-582 

. 582 
. 582 

. 582 
. 582 

. 582 
. 582 



INDEX TO APPENDIX. 



A, ... 

Absorption, Luminous . 

Adhesion, Electric 

Adjustable Condenser, . 

Adjustable Vacuum, Crookes', Tube 

Adjustment of Skew Carbons, 

Admittance, 

Aging of Resistance Coils, . 

A.I. E. E., 

Air Expansion, Lightning Arrester 

Air, Magnetic Circuit . 

Alternating Current, Rectifier 

Alternations, Co-pbasal 

Alternative Discharge, 

Alternator, Diphase . 

Alternator, Monocyclic 

Alternator, Multiphase 

Alternator, Pitch of 

Alternator, Triphase . 

Alternator, Uniphase 

American Wire Gauge, 

Ammortisseur, 

Ampere Gauge, . 

Ampere, International, 

Amyloid, 

Analogy, Hydraulic 

Anchor, Composite Pole 

Anchor Guy, Stub . 

Anchor Pole, .... 

Anchoring of Trolley Line, . 

Angle of Lag, .... 

Anode, Preponderating 

Anticathode, .... 

Anti-Hum, 

Anti-Magnetic Watch, 

Anti-Parallel, Feeding . 

Arc Deflector, .... 

Armature, Toothed-Ring 

Arm, Cross 

Arm Cross Brace, .... 

Arm Rest, . . . 

Arrester, Lightning, Air Expansion 

Arrester, Lightning, High Resist- 
ance 

Arrester, Lightning, Non-Arcing 

Arrester, Lighting, Swinging Ball 

Artificial Line, .... 

Attaching Plug, .... 

Automatic Magnetic, Circuit 
Breaker 

Automatic Paper Winder, 



Page. 
583 
5S3 
588 
592 



621 
583 

61S 
583 
608 
609 
616 
593 
595 
583 
583 
5S4 
613 
584 
584 
631 
584 
601 
584 
5S4 
5S4 
613 
622 
585 
585 
606 
5^5 
585 
5S5 
630 
599 
585 
585 
594 
581 
585 



60S 
608 
608 
613 

591 

612 



Automatic Switch, 

Automatic Telephone Exchange 

Automatic Telephone Switch 

Automatic Transmitter, 

Auto-Transformer, 

Awning Insulator, . 



Page. 



Back, Carbon . 

Balance, Candle . 

Balance Indicator, 

Balanced Metallic Circuit, 

Ball, Electric, Time 

Ball Lightning, . 

Balls, Carbon . 

B. and S. G., 

Barrow, Wire . 

Bar, Tamping 

Bath, Oil . 

Baton, Electric 

Battery Insulator 

Battery Switch, , 

Beaded Cable, . 

Becquerel Rays 

Bimetallic Wire 

Bipolar, . . . . 

Birmingham, Wire Gauge 

Bismuth Spiral, 

Blackening of Lamp Bulbs, 

Block, Ceiling 

Board, Distributing 

Board, Legging-key 

Board, Panel . 

Bond, Rail . 

Bone of Horus, 

Booster, 

Booth, Telephone . 

Border Lights, 

Bouchenzing Process, 

Box, District Call 

Box, Section 

Box, Shunt, Compensated 

Box, Stage 

Box Starting 

Box, Universal Shunt 

Box, Wall 

Brace, Cross Arm . 

Bracket Curve, 

Break- Wheel, . 

Bridges, 



6y6 



INDEX TO APPENDIX. 



Bridge, Conductivity 
Bridge, Cylindrical 
Bridge, Decade 
Bridle, .... 
Brown and Sharpe Gauge, 
B. T. U., 
Bulb, Lamp 
Bunch Lights, 
Burnettizing Process, 
Bushed Poles, 
Bushing, Socket 
Button, Carbon 
Button, Ceiling 
Butt-prop, 



C, . . . . 

Cable, Beaded 

Cable, Core-ratio of 

Cable, Emergency . 

Cablegram, . 

Cable Head, 

Cabinet, Silence . 

Cabinet, Sound Proof Teleph 

Call Box, District 

Calorimotor, 

Candelabra Receptacle, 

Candle Balance, 

Canopy, 

Canopy Switch, 

Cant-Hook, . 

Capability, Electrical, of Voltai 

Cell 
Carbon Back, . 
Carbon Balls, 
Carbon Button, 
Carbon Diaphragm, 
Carbons, Skew Adjustment 
Carcass of Dynamo, 
Carriage Pen, . 
Cathetometer, 
Cathode, .... 
Cathode, Preponderating 
Cathodic Rays, 
Catoptrics, . 
Cazin, .... 
Ceiling Block, 
Ceiling Button, 
Ceiling Rosette, . 
Cell, Heat 
Cell Tester, . 
Cements, Insulating 
Center of Distribution, 
Centre Pole. 
Chandelier Switch, 
Checking Instrument, 
Chemic, 

Chronoscope, Electric . 
Circuit Breaker, Automatic 

netic 
Circuit Breaker, Vacuum 
Circuit, Magnetic Air 
Circuit, Magnetic, Closed 



Mag 



rage. 
. 592 

594 
. 587 

605 
. 631 

58T 
. 606 

5S8 



588 
589 
588 
595 

588 
588 
663 
588 
588 
589 



589 
5d5 
616 
589 
598 
623 
589 

589 
589 
589 

5S9 
590 
621 
590 
612 
590 
590 
590 
615 
590 
590 
619 
588 
619 
590 
626 
605 
596 
613 
623 
590 
590 
590 

591 
591 
609 
609 



Page. 

Circuit, Metallic, Balanced . . 586 

Clamp, Feeder .... 599 

Clip, Feeder 599 

Closed Magnetic Circuit, . . 609 

Coherer, .... * 591 

Coil, Compensating . . . 592 

Coil, Damping .... 591 

Coil, Tesla 592 

Coils, Resistance, Aging of . 618 

Combination Fixture, . . . 599 

Combination Switch, . . . 623 

Commutation, Switch . . . 624 

Comparative Indicator, . . 592 

Compensated Shunt Box, . . 620 

Compensating Coil, . . . 592 

Compensator, 58T 

Composite Anchor Pole, . . 613 

Composite Wire, .... 630 

Condenser, Adjustable . . 592 

Condenser, Multiple-series, . . 592 

Condenser, Sub-divided . . 592 

Conductivity Bridge, . . . 592 

Conductor, Twin, ... 592 

Conduit, Flexible .... 592 

Conduit, Interior . . . 593 

Conduit, Railway .... 593 

Conduit, Rodding a 619 

Constant-current Motor, . . 610 

Constant-potential Motor, . 610 
Construction of Switch Board, 

Edgewise System . . . 59T 

Contact Maker, .... 593 
Continuity Preserving Transmitter, 626 

Continuous Rheostat, . . . 618 

Co-phasal Alternations, . . . 593 

Core Pins 593 

Core-ratio of Cable, . . . 593 

Cosine Law of Illumination, . 603 

Coulomb, International . . . 693 

Coupling, Electric . . . 594 

C 2 R, Loss 609 

Crookes' Adjustable Vacuum Tube, 628 

Crookes' Focus Tube, . . . 628 

Crookes' Tube, . . . 627 

Cross Arm, 594 

Cross Arm, Brace . . . 587 

Cross-over, 594 

Cryptoscope, .... 594 

Cups, Leading-in . ' . . . 594 

Current, Marking . 594 

Current Reorganize^ . . . 597 

Current, Spacing .' . . 594 

Current Tap, 594 

Curve Bracket 614 

Curve Tracer, Ewing's . . .594 

Cut-out Film, .... 594 
Cut-out, Fixture . . . .594 

Cut-out, Magnetic ... 591 
Cylindrical Bridge, . . .594 

Damping, Coil .... 591 

Dart, 594 



INDEX TO APPENDIX. 



677 



Page. 

Dead Beat Galvanometer Plug, . 600 

Dead-end, 594 

Dead-man, 595 

Decade Bridge, 587 

Deflagrator 595 

Deflector, Arc .... 5S5 
Detector, Phase . . . .612 

Device, Electro-receptive . 595 

Device, Translating . . . 595 

Dextrorsal, ..... 595 

Diagram, Load .... 608 

Dial, Instrument, Illuminated . 603 

Diaphram, Carbon .... 590 

Dimmer, Theater ... 595 

Dioptrics, 595 

Diphase, Alternator . . . 583 

Diphaser, 583 

Discharge, Alternative . . 595 

Discharge, Tesla .... 596 

Disc, Retarding, .... 618 

Distributing Board, . . . 596 

Distribution, Center of . . 596 
Distribution, Electrical Efficiency of 596 
District Call Box, . . . .589 

Door Trigger 596 

Door Trip, Electric . . .596 

Double Balanced, Relay . . 617 

Double Throw, Switch . 624 

Drift of Needle, .... 596 

Dynamic Electro, Induction . 603 

Dynamo, Carcass of . . . 590 

Dynamo, Heteropolar . . 596 

Dynamo, Homopolar . . . 596 

Dynamo, Motor .... 597 

Dynamo, Multi-circuit 596 

Dynamo, " Non-polar" . . 596 

Dynamo, Steam .... 622 

Dynamotor, 597 

E, 626 

Earthkin, . . . . . 626 
Edgewise System of Switch Board 

Construction 597 

Edison Wire Gauge, ... 631 
Efficiency of Electrical Distribution, 596 

Efficiency of Lamp, . . . 607 

Efficiency, Torque, Apparent . 597 

Efficiency, Torque . . . 597 

Elbow Rest 585 

Electrical Capability of Voltaic Cells 589 
Electrical Efficiency of Distribu- 
tion, 596 

Electrical Engineer. . . . 598 

Electrically Illuminated Fountain, 6<>0 
Electric Adhesion, . . .583 

Electric Baton, .... 586 

Electric Chronoscope, . . . 590 

Electric Coupling, . . 594 
Electric Door Trip, . . .596 

Electric Elevator Signal, . 597 

Electric Gas Lighting, Torch . 627 

Electrician, 597 



Page. 
Electric Igniter, . . . .603 
Electric Insulation, . . . 605 
Electric Meteorgraph, , . 610 

Electric Plate Stove, . . . 613 
Electric Search Light, . . 619 

Electric Shoe, 620 

Electric Sign, .... 621 
Electric Source, .... 621 
Electric Sunshine Recorder, . 623 
Electric Time Ball, . . . 626 

Electric Wand, .... 627 

Electrobat, 597 

Electrocution, . . . . 598 
Electro-dynamic Induction, . . 603 

Electrograph 598 

Electrolabrum, . . . .598 

.Electrolier Switch, ... 624 
Electro-magnet, Portative . . 598 
Electro-magnet, Tractive . . 598 
Electro-receptive Device, . . 595 
Electrothanatosis, . . . 598 

Electrotherm, 598 

Electrotisis, .... 

Electrozemia, . 

Elevator Signal, Electric . 

Emergency Cable, . 

E. M. F., .... 

Emissivity, 

Enamel, Rheostat 

Enclosed Arc Lamp, 

End Connectors, . 

Engineer, Electrical 

Entrefer 

Exchange, Automatic Telephone 

Exploder 

Ewing's Curve Tracer, . 



F\ cF 

Factor, Impedance 
Factor, Load . 
Factor, Reactance 
Farad, International 
Feeder Clamp, 
Feeder Clip, 
Feeding, Anti-parallel 
Fibre, Vulcanized . 
Figures, Magnetic 
Filament, Squirted . 
Film, Cut-out 
Fixture, Combination 
Fixture, Cut-out . 
Flaming, . 
Fleming's Hand Rule, 
Flexible Conduit, . 
Flicker, Photometer 
Floor Insulator, 
Fluorescent Screen, 
Fluoroscope, . 
Flush Switch, 
Fountain, Electrically 
Fuse, Wire . 



598 
597 
588 
598 
598 
618 
607 
598 
598 
598 
598 
603 
594 

599 
599 
609 
599 
599 
599 
599 
599 
599 
609 
599 
594 
599 
594 
599 
602 
599 
613 



600 
600 
. ' 624 
Illuminated 600 
630 



678 



INDEX TO APPENDIX. 



Galvanometer, Helmholtz 
Galvanometer, Lecture 
Galvanometer, Oil Vessel 
Galvanometer Plug, Dead Beat 
Galvanometer, Speaking 



Page. 

. 600 
600 

. 600 
600 
600 



Galvanometer, Tangent, Universal 601 
Galvanometers, Rotating Stand for 621 
Gas Lighting, Electric Torch . 627 
Gauge, Ampere . . . . 601 
Gauge, Brown & Sharpe . . 631 
Gauge, Edison, Wire ... 631 
Gauge, Wire, Birmingham . .631 

Gauss 601 

Geissler Tube, Rotator . . .619 

Gilbert 601 

Grothuss' Hypothesis, . . .601 
Ground Detector, ... 601 
Ground Indicator, .... 601 
Guard, Lamp .... 60T 
Guard, Running Wires . . .631 

H, GTl 602 

Hand Rule. Fleming's . . .602 

Head, Cable .... 589 

Heat, Cell 590 

Heat, Indicating, Paint . 611 

Helmholtz, Galvanometer . . 600 

Hertz's Oscillator, ... 611 

Hertz's Radiator, . . . .611 

Heteropolar Dynamo, . . 596 
•High Resistance Lightning Arrester, 608 

Homopolar Dynamo, . . . 596 

Horus, Bone of, . . . . 603 

Human Relay Working, . . 603 

Humming of Transformer, 603 

Hydraulic Analogy, . . 584 

Hypothesis, Grothuss' . . 601 

Igniter, Electric . . . .603 

Illuminated Dial Instrument, . 603 

Illuminated Electrical Fountain, 600 

Illumination, Cosine Law of . . 603 

Impedance Factor, . . 599 

Independent Vibrator, . . . 629 

Indicating Heat, Paint . . 611 

Indicating Push Button, . . 614 

Indicating Switch, . . . 624 

Indicator, Balance . . . 586 

Indicator, Comparative . 592 

Indicator, Ground . . . 601 

Indicator Light, .... 607 

Indicator Pole, . . . .613 

Indicator, Pressure . . 614 
Individual Signal, .... 621 

Induction, Electro-dynamic . 603 

Induction, Magnetic Lines of . 609 

Induction Plate, .... 603 

Insulating Cements, . . . 605 

Insulating Joint, .... 605 

Insulating Table, . . . .605 

Insulation, Electric ... 605 



Insulation, Puncturing 
Insulator, Awning 
Insulator, Battery . 
Insulator, Floor, . 
Insulator, Pull-off . 
Insulator, Section 
Insulator, Strain 
Insulator, Transposition 
Instrument, Checking 
Instrument, Illuminated 
Instrument, Zero 
Intake, .... 
Interior Conduit, 
Intermediate Switch, . 
International Ampere, 
International Coulomb, 
International Farad, 
International Ohm 
International Volt, . 

Joint/Insulating 
Joint, Paste . 
Joint, Sleeve 
Jumper, 



Dial 



Key, Mouth . 

Key, Multiple . 

Key, Pistol . 

Key, Reaction . 

Key Runners 

Key, Signaling 

Key, Strap 

Key, Successive Contact 

Key, Switch . 

Key, Touch 

Konstantan, . 



of 



Page. 
. 614 

604 
. 604 

604 
. 614 

604 
. 604 

604 
. 590 

60S 
. 632 

605 
. 593 

624 
. 584 

593 
. 599 

611 
. 629 

. 605 
605 

. 605 
605 



605 



I*. 

Lag, Angle of 
Lamp Bulb, 

Lamp Bulbs, Blackening 
Lamp, Efficiency of 
Lamp, Enclosed Arc . 
Lamp Guard, . 
Lamp Stand and Scale, 
Lamp, Theater 
Leading-in Cups, 
Lecture Galvanometer, 
Legging-Key Board, . 
Light Indicator, 
Lightning Arrester, Air Expansion 
Lightning Arrester, High Resist- 
ance 

Lightning Arrester, Non-Arcing 
Lightning Arrester, Swinging Ball 
Lightning, Ball .... 
Lighting, Gas Electric, Torch . 
Lighting, Vacuum Tube 
Lights, Border .... 

Lights, Bunch 

Line, Artificial .... 



606 
606 
606 
606 
606 
606 
624 
606 
606 



606 
606 
607 
607 
607 
607 
607 
607 
594 
600 
607 
607 
608 



608 
608 
5S6 
627 
607 
587 
588 
608 



IXDEX TO APPENDIX. 



679 



Line, Wind and Water . 
Lines of Magnetic Induction 
Load Diagram, 
Load Factor, 
Load, Peak of . 
Lock Switch, 
Loss, C 2 R . 
Luminescence, 
Luminous Absorption, 



. 911 



Ci 



m 

Magnet, Striking 
Magnet Winder, . 
Magnetic, Automatic 

Breaker 
Magnetic Circuit, Air 
Magnetic Circuit. Closed 
Magnetic Cut-out, 
Magnetic Figures, . 
Magnetic Induction, Lines 
Magnetic Phantom, 
Magnetic Source, 
Magnetic Spectrum, 
Magnetic Tester, 
Magnetite, 
Main, Vertical 
Manual Translation, 
Marconi's Relay, . 
Marker, Time . 
Marking Current, 
Metal. Non-Arcing 
Metallic Circuit, Balanced 
Metallic Reluctivity, 
Meter, Telephonic 
Meteorograph, Electric . 
Metronome, Registering 
Micanite, .... 
Mil-ammeter, 
Milliammeter, . 
Milli-amperemeter, 
Mitis Metal, 
M. M. F., 

Monocyclic Alternator, . 
Motor, Constant-current, 
Motor, Constant-potential 
Motor, Dynamo . 
Motor, Pilot, . 
Mouth, Key . 
Multicellular Voltmeter, 
Multi-circuit Dynamo, 
Multiphase Alternator, . 
Multiphaser, 
Multiple Key, . 
Multipler for Voltmeter, 
Multiple-series, Condenser 
Municipal System, 

If, f, ... 

Napoli's Photometer, 
Needle, Drift of . 



of 



Page. 
. 60S 

609 
. 608 

609 
. 609 

624 
. 609 

609 
. 583 

609 

. 622 
630 

. 591 

609 
. 609 

591 
. 609 

609 
. 609 

621 
. 609 

626 
. 6C9 

619 
. 603 

611 
. 62T 

59-4 
. 610 

5S6 
. 618 

610 
. 610 

610 
. 610 

610 
. 610 

610 
. 610 

610 
. 583 

610 
. 610 

597 
. 610 

605 
. 629 

596 
. 581 

584 
. 606 

611 
. 592 

611 



613 
596 



Non-Arcing Lightning Arrester 
Non-Arcing, Metal 
Non-Magnetic Watch, 
''Non-Polar" Dynamo, 

O, 

Oersted, .... 

Ohm, International 

Oil Bath, .... 

Oil Vessel Galvanometer, . 

One-Coil Transformer, . 

Oscillator, Hertz's 

Ozokerite, 



I», $ 



Paint, Heat Indicating . 
Panel Board, 

Paper Winder, Automatic 
Paste Joint, .... 

Peak of Load, . 
Pen Carriage, 
Pendant Pull, Switch 
Permittance, 
Phantom Magnetic, 
Phase Detector, . 
Phase, Splitting the 
Photo-Chronograph, Polarizing 
Photo-Fluoroscopy. 
Photometer, Flicker . 
Photometer, Napoli's 
Phonogram, .... 

Phonoplex Telegraphy, . 

Pilot Motor, 

Pin, ...... 

Pins, Core, .... 

Pistol, Key .... 

Pitch of an Alternator 

Plate, Induction 

Plate Stove, Electric . 

Plug, Attaching 

Plug, Galvanometer Dead Beat 

Pneumatic Rodding, 

Point, Smashing . 

Polarizing, Photo-Chronograph 

Pole, Anchor 

Pole, Center, .... 

Pole, Composite Anchor 
Pole Indicator, 

Pole Top 

Poles, Bushed .... 
Portative, Electro-Magnet 
Prefixes of Scientific Units, . 
Preponderating Anode, 
Preponderating Cathode, 
Pressure Indicator, 
Process, Boucherizing . 
Process, Burnettizing . 
Projector, .... 
Pull-off Insulator, 
Pull-over, 
Puncturing of Insulation, . 



68o 



INDEX TO APPENDIX. 



Page. 

Push-Button, Indicating . . 614 
Push-Button, Switch ... 625 
Push, Sounder 614 



Quadmeter, 
IT, cH 



Radiator, . 

Radiator, Hert/.'s 

Radiograph, 

Radiography, 

Radio-micrometer, 

Rail, Bond . 

Railway Conduit, 

Rake, . 

Rays, Becquerel 

Rays, Cathodic . 

Rays, Rontgen 

Rays, X 

Reactance, 

Reactance Factor, 

Reaction, Key 

Receptacle, . 

Receptacle, Candelabra . 

Recorder, Sunshine, Electric 

Rectifier, Alternating Current 

Registering Metronome, 

Regulating Socket, 

Relay, Double Balanced 

Relay, Human Working 

Relay, Marconi's . 

Reluctancy, 

Reluctivity, 

Reluctivity, Metallic 

Reorganizer, Current . 

Resistance Coils, Aging of 

Resistance, Specific 

Resistivity, 

Resonator, Sounder . 

Rest, Arm 

Rest, Elbow . 

Retarding Disc, 

Rheostat, Continuous 

Rheostat, Enamel . 

Ring, Toothed Armature 

Riser, .... 

Rodding a Conduit, 

Rodding, Pneumatic 

Rontgen Rays, 

Rosette, Ceiling 

Rotary Transformer, 

Rotating, for Galvanometer, Stand 

Rotator, Geissler Tube . 

Rotor, 

Runners, Key . 
Running Guard Wires . 

Scale and Lamp Stand, 
Scientific Units, Prefixes of 
Screen, Fluorescent 
Sealing-in 



514 

614 

615 
611 

615 
615 
615 
587 
593 
615 
615 
615 
616 
616 
616 
599 
606 
616 
616 
623 
616 
610 
617 
617 
603 
617 
618 
618 
618 
597 
618 
618 
618 
618 
585 
585 
618 
618 
618 
585 
619 
619 
619 
616 
619 
597 
621 
619 
619 
606 
631 

607 
614 
600 
619 



Pape. 
Search Light, Electric . . .619 

Secohmmeter, .... 620 

Section Box 620 

Section Insulator, ... 604 

Selector Signal, .... 621 

Selector Volt 629 

Self-Regulating Crookes' Tube, . 628 

Shoe, Electric .... 620 

Shunt Box, Compensated . . 620 

Shunt Box, Universal . . . 620 

Siebrosal, 620 

Signal, Electric Elevator . . 597 

Signal, Individual .... 621 

Signal, Selective .... 621 

Signaling Key, .... 606 

Sign, Electric .... 621 

Silence Cabinet, .... 627 

Sinistrorsal, 621 

Skew Adjustment of Carbons, . 621 

Skiagraph 615 

Sleeve Joint, 605 

Smashing Point, .... 621 

Socket, Bushing .... 588 

Socket, Regulating . . . 617 

Sounder Push, .... 614 

Sounder, Resonator . . . 618 

Soundproof Telephone Cabinet, 626 

Source, Electric .... 621 

Source, Magnetic .... 621 

Spacing, Current .... 594 

Span Guard Wires, .... 681 

Span Wires, .... 632 

Speaking Galvanometer, . . 600 

Specific Resistance, . . . 618 

Spectrum, Magnetic . . . 609 

Spiral, Bismuth .... 586 
Splitting the Phase, . . .621 

Squirted Filament, ... 599 

Stage Box, 621 

Stand, Rotating, for Galvanometer 622 

Starting Box, 622 

Stator, 622 

Steam Dynamo 622 

Steno-Telegraphy, . . . 622 

Stove, Plate, Electric , . . 613 

Strain Insulator, .... 604 

Strap Key, 606 

Striking Magnet, .... 622 

Strut, . . . . . .622 

Stub, Anchor Guv ... 622 

Sub-divided Condenser, . . . 592 

Sub-station, . . . . . 622 

Successive Contact Key, . . 606 

Sunshine Recorder, Electric . 623 

" Superior," Wire .... 632 

Swinging Ball, Lightning Arrester 608 

Switch, Automatic . . . 623 

Switch, Automatic Telephone . 623 

Switch, Battery . . . . 623 

Switch Board Construction, Edge- 
wise System .... 597 

Switch, Canopy .... 623 



INDEX TO APPENDIX, 



68 1 



Switch, 
Switch, 
Switch, 
Switch, 
Switch, 
Switch, 
Switch, 
Switch, 
Switch, 
Switch, 
Switch, 
Switch. 
Switch 
Switch 
System 



Chandelier . 

Combination . 

Commutation 

Double Throw 

Electrolier . 

Flush 

Indicating . 

Intermediate . 

Key . 

Lock 

Pendant Pull 

Push Button . 
Throw-Over, 

Voltmeter, 
, Municipal 



Table, Insulating- 
Tachometer, 
Tailings, 

Tamping Bar, 

Tangent, Universal Galvanometer 

Tap, Current 

Telegram, 

Telegraphy, Phonoplex 

Telegraphy, Wireless 

Telephone, Automatic Exchange 

Telephone, Automatic Switch 

Telephone Booth, . 

Telephone Cabinet, Soundproof 

Telephonic Meter, . 

Terella, 

Tesla's Coil 

Tesla Discharge, . 

Test Board, 

Tester, Cell . 

Tester, Magnetic 

Testometer, . 

Tetrapolar, 

Theater Dimmer, 

Theater Lamp, 

Thermo-galvanom eter, 

Throw-over Switch, 

Time Ball, Electric 

Time Marker, .... 

Tie, Wire .... 

Toothed Ring Armature, 

Top, Pole .... 

Torch, Electric Gas Lighting 

Torque, Apparent Efficiency 

Torque, Efficiency 

Touch Key, 

Tracer, Ewing's Curve . 

Tractive, Electro Magnet . 

Transformer, Humming of 

Transformer, One-Coil 

Transformer, Rotary 

Translating Device, 

Translation, Manual 

Translator 

Transmitter, Automatic 
Transmitter, Continuity Pre- 
serving, .... 



Page. 
. 623 

623 
. 624 

624 
. 6-24 

624 
. 624 

624 
. 624 

624 
. 625 

625 
. 625 

625 
. 611 



605 
625 
625 
5S6 
601 
594 
625 
612 
625 
598 
623 
626 
626 
610 
626 



626 
626 
626 



595 
60T 
626 
625 
626 
62T 
632 
585 
613 
627 
595 
59T 
606 
594 
598 
603 
586 
59T 
595 
603 
62T 
627 

62T 



Transposition, Insulator 
Transposition Wires, 
Trigger, Door . 
Trimming, .... 
Trip, Electric Door 
Triphase, Alternator, 

Triphaser, 

Trolley Line, Anchoring of . 
Tube, Crookes' . . . . 
Tube, Crookes' Adjustable 

Vacuum .... 
Tube, Crookes' Focus . 
Tube, Crookes' Self-Regulating 

Tubulating, 

Turbo-alternator, . 
Turbo-generator, 
Twin Conductor, 



Page. 

604 
. 627 

596 
. 627 

596 
. 584 

584 
. 585 

627 



628 



628 
592 



U, 584 

Uniphase Alternator, . . . 584 

Uniphaser, 584 

Units, Scientific Prefixes . . 614 

Universal Galvanometer, Tangent 601 
Universal Shunt Box, . . .620 

V, 591 

Vacuum, Circuit Breaker . . 591 

Vacuum Tube, Crookes' Adjustable 628 

Vacuum Tube Lighting, . . 607 

Vertical Main, 619 

Vibrator, Independent . . 629 

Voltaic Cell, Electrical Capability 589 
Volt-ammeter, 



Voltance, .... 


. 629 


Volt, International 


629 


Voltmeter, Multicellular 


. 629 


Voltmeter, Multipler for 


611 


Voltmeter Switch, . 


. 625 


Volt Selector, 


629 


Volume, Winding . 


. 630 


Vulcanized Fibre, 


599 


w, 




Wall-box 


629 


Wall Socket, . 


. 616 


Wand, Electric, . 


627 


Watch, Anti-magnetic . 


. 630 


Watch, Non-magnetic 


630 


Water and Wind Line, . 


. 608 


Weber 


630 


Working, Human Relay 


. 603 


Wind and Water Line, 


608 


Winder, Magnet 


. 630 


Winding Volume, 


630 


Wire, Annunciator . 


. 630 


Wire Barrow, 


586 


Wire, Bimetallic 


. 630 


Wire, Fuse .... 


630 


Wire Guage, American . 


. 631 


Wire Guage, Birmingham . 


631 


Wire, Composite 


. 630 


Wire Gauge, Edison . 


631 



682 



INDEX TO APPENDIX. 



Page. 

Wire Office, 631 

Wire, " Superior " . 632 

Wire, Tie 632 

Wireless Telegraphy. 625 

Wires, Running Guard . . .631 
Wires, Span .... 631 



Wires, Span Guard . 
Wires, Transposition 

XRays, . 



25ero Instrument, 



Page. 

. 632 

62T 

. 616 

632 












I 



